So having seen some doubles tournaments around my area, the subject has been raised in my mind and gotten me thinking about how best to abuse (in an enjoyable way, of course) such a system. Such a tournament offers a lot of possibilities for unique stuff, but also will depend a lot on what sort of rules are used.
The real overall issue with doubles is one of filling roles and covering weaknesses. Each codex has its own ups and downs, so if you want to maximize the strength of your doubles team, you need to find two books that suit each other well and can fill holes that the other codex has.
For this initial section, I'll be assuming the following rules. (More discussion on how other rules change things will come later.) I should also note that this is mostly theoretical and experimental in nature; I would welcome other ideas on the subject. In any case, the strictures:
-1000pts per player, two players; FoC separate for each person
-Units on a team are "friendly" with each other, but are not considered to be in the same army
-Teams may not share transports and ICs may not attach to the other player's squads
-Turns are simultaneous for both players on a team
These are fairly common rules from what I've seen, with the most usual changes being the FoC (some tournaments have the players share it, or parts of it) and "friendliness" (some tournaments allow using each other's ICs/transports, others don't allow aura-sharing at all.)
The big obvious point here, as alluded to above, is auras. These rules allow you to gain/combine auras and abilities from different codices, which is absolutely HUGE. This makes armies with powerful continuous or activated buffs, such as Blood Angels, Grey Knights, Tyranids, Eldar, and Orks, primary contenders for at least one of the slots in a list, and quite possibly both. So how about a once-over to see what each of the books gives us?
Black Templars: Well, they can bring some pretty efficient MSU shooting and their Typhoons are nice, but in general I don't think they're a great choice. You will be required to run a Champion in this army, which will eat up a lot of your points.
Blood Angels: This is the cool kid in town; any other army is going to have to look to BA when saying "how do I measure up to the field?", because the ability to give both halves of the army FNP is incredibly powerful. BA also brings speed and abundant Melta as well as some psychic defense to the party and encourages the team towards and aggressive strategy.
Chaos Space Marines: Sadly, there isn't a lot they can do that someone else can't do better. Lashes are cute, but is that gonna carry both halves of the army? Probably not. Pick a different Marine codex instead, get bonus features with your upgrade.
Daemons: If the other half of the army can bring overwhelming AT firepower, maybe you might think about running Daemons. But no, don't. Just... don't.
Dark Angels: With lackluster versions of the vanilla codex, DA are forced to rely on special character unlocks to bring good armies- and with only 1000pts to work with, this can be very, very limiting. As a result, I think DA are one of the low-end choices for a doubles tourney, as there really isn't much they can do that someone else can't do better. 4x5 Terminators and Belial is... just not that impressive.
Dark Eldar: If the other army can bring a similarly offense-oriented playstyle and has enough resilience to compensate for DE's glass hammer approach, I think they can be a good partner despite their lack of synergy abilities. Many of the things that DE get abundantly and cheaply are hard to come by in other armies, so they do an excellent job of playing half of an equation.
Eldar: EDIT Derp. I guess Guide and Fortune can only be applied to Eldar units, so Doom is your only useful power. Fire Dragons and Wraithlords are neat, but they aren't enough on their own, I don't think.
Grey Knights: Although most of their abilities give no benefit to their ally, bar a Librarian, GK are a prime recipient for many people's ability to hand out bonuses. They also benefit from having a partner with long-range weaponry and cheap home-field units, both of which they have few choices for. Since they are able to play shooty or choppy, aggressive or defensive, they are very flexible when partnering up.
Imperial Guard: Although IG only has a few auras (most notably the Lord Commissar and Straken's), they certainly bring plenty of other benefits from the field. Barring a ruling otherwise, Orders can be issued to non-IG units on your side (since nowhere in the description does it explicitly reference Guard units, nor is the ability to receive them a special property of Guard units.) With the higher Ld values many other armies have, they can easily pass Orders given to them, though the degree to which they benefit from them may vary. Even that aside, however, IG's efficient firepower and expensive blast/template weaponry makes it a prime candidate for many combinations.
Necrons: Suppression fire and anti-infantry are Necrons' specialties, along with being tough as all get out. Necrons with FNP is a scary prospect, as is shutting down an enemy shooting phase at a key moment with Solar Pulse. Probably works well paired up with something that can bring good AT that wants to give cover to vehicle hulls (hint: Tau and DE.)
Orks: Orks bring two main tricks to the party: the Kustom Force Field (5+ cover, 4+ for vehicles, at all times) and cheap, efficient troops. When limited to their own codex Boyz suffer from a lack of support, but combined with others their low price and ability to hurt many targets go up in value a lot. Obviously a mechanized list with Battlewagons is very strong, but hybrid and infantry lists have some possibilities as well, which is a major divergence from pure Ork lists- other armies can provide the mobility and AT that a Green Tide list lacks.
Sisters of Battle: Unfortunately, SoB don't have a ton to offer their friend. Dominions are still excellent and you'll take them and Melta and Flamers can be found all through the codex, but your basic troops are expensive and your HQs don't fit the purpose of your army well. The girls are unlikely to make a strong appearance compared to the other codices around, mostly just due to their mini-dex being rather bad.
Space Marines: With only the Librarian really bringing any broad-reaching benefits, Space Marines are only a middling choice for a doubles list, all the more so because Tacticals, while not bad, are hardly something you're busting down the door to get.
Space Wolves: Although they don't provide much (Storm Caller and Saga of Majesty being about it) to the partner, SW can be excellent recipients for many abilities, all the more so because they fit into the aggressive mold that several other such armies mesh well with. The smaller points limit per player means that the FoC limit on Long Fangs means less to you, which makes them a very strong fire support option.
Tau: Unfortunately you can't share your Markerlights with non-Tau, otherwise Tau would be a top-ranked army along with BA. However, you can bring a devastating anti-tank shooting force with Tau and your buddy can bring melee defense and/or other support, so they have definite possibilities there. Look to having a partner than can benefit from your mobile cover (i.e. Devilfishes) and/or that can distract shooting away from your vulnerable Crisis and Broadsides. If you can somehow get Ld that doesn't suck, that would be nice, too.
Tyranids: Tyranids get a huge leg up in doubles games for one reason: you can make your partner bring the anti-tank. With that problem solved, Tyranids become hugely more viable; you can consider Ymgarl for disruption or Venomthropes to provide support (they give cover to anything, even tanks.) Speaking of tanks, you'll have actual tanks to hide your models behind, which is also huge for Tyranids- Venomthropes, Hive Guard, and Biovores all become a lot more scary when they can't be shot at. Catalyst and Onslaught are very helpful support abilites, as is Paroxysm, so Tyranids are a distinct contender in doubles games, or at least much more so than usually.
Basic Tactics
The most fundamental decision you have to make when writing a doubles list is simple, but lies at the heart of all list-building: do you want to try and overload the enemy with one thing (e.g. two assault armies, etc) or diversify yourself so you have multiple options (e.g. a shooting army supporting an assault army.) Neither one is necessarily wrong, but it's important to remember that whatever you may choose to do, you should have some support of all types available. A pair of shooting armies need to have a plan for when the enemy reaches melee; a pair of assault armies should have ways to hurt the enemy at range. Just as with "normal" list-writing, you cannot afford to simply concede an entire strategy to the enemy and assume that you will be fine.
Thus, just as with any other army, your doubles lists will need to find ways to make sure that they have all avenues covered without unduly diluting your main strategy- the eternal challenge of list-writing. Given that most all doubles tournaments are fairly large (almost always over 1500pts, more commonly 2000pts or more) you should expect to see all sorts of things on the table across from you, from Land Raiders to Nobz to Tyrantstars to massed vehicle hulls. Make sure your own team has a plan for all contingencies: can you chase down a bunch of fast skimmers? Can you survive and retaliate against an all-Deep Strike list? Can you outmaneuver and whittle down a horde? Just as the list possibilities for your team are endless, so are the enemy's- and remember, they can pull just as many dirty tricks as you.
Combinations
BA/GK: Bring lots of tanks with squads inside, FNP on everything, psychic defense galore, long- and short-range shooting... geez, what else do you want? Oh, melee defense? Yeah, they have that, too, and your guys are striking ahead of everyone else with Power Weapons and all kinds of other nonsense. These two armies complement each other very, very well.
1 Librarian (Shield, Lance)
2 Sanguinary Priests (1 Combi-Melta)
5 ASM (Melta, LasPlas Razor)
5 ASM (Melta, LasPlas Razor)
5 ASM (Melta, LasPlas Razor)
5 ASM (Melta, LasPlas Razor)
5 ASM (Melta, HF Razor)
1 Xenos Inquisitor
5 Purifiers (2 Psycannon, Psyback)
5 Purifiers (2 Psycannon, 2 Halberd, Psyback)
5 GKSS (Psycannon, Psyback)
5 GKSS (Psycannon, Psyback)
1 Psyfleman
1 Psyfleman
BA/SW: Two aggressive MEQ armies that bring duality in every single unit and support shooting wherever they want/need it. SW can bring more bodies and are a overall a little better in a fight (thanks to Counterattack and Wolf Standard), but BA bring force multipliers and multiple special weapons to the party. And who doesn't love staring down a billion missile shots from the backfield?
1 Librarian (Shield, Sword)
3 Sanguinary Priests (1 CombiMelta)
5 ASM (Melta, Infernus, PW, HF Razor)
5 ASM (Melta, Infernus, PW, HF Razor)
5 ASM (Melta, Infernus, PW, HF Razor)
5 Devs (4 Missile)
5 Devs (4 Missile)
1 Rune Priest (Lightning, Hurricane)
9 GH (Melta, Standard, Rhino)
9 GH (Melta, Standard, Rhino)
9 GH (Melta, Standard, Rhino)
5 LF (4 Missile)
5 LF (4 Missile)
5 LF (4 Missile)
IG/Tau: IG brings the things Tau don't really have access to: Melta, Ld10 auras, and blasts/templates. Tau just bring a crapload of guns and utility and hide their scrawny butts behind all the cover IG provides.
1 Lord Comissar (Camo Cloak)
6 Psyker Battle Squad (Chimera)
6 Psyker Battle Squad (Chimera)
Infantry Platoon
-PCS (4 Flamer, Chimera)
-Infantry Squad (Autocannon, Melta)
-Infantry Squad (Autocannon, Melta)
-Infantry Squad (Autocannon, Melta)
1 Vendetta (HBs)
1 Vendetta (HBs)
1 Hydra
1 Shas'el (MP, PR, MT)
2 Crisis (MP, PR, MT)
6 FWs
10 Kroot (2 Hounds)
8 Pathfinders (Devilfish w/DP)
2 Broadsides (ASS)
2 Broadsides (ASS)
2 Broadsides (ASS)
Tyranids/Tau: Tau excel at wrecking vehicles; they have Railguns, Missile Pods, Fusion Blasters and Markerlights to make them tank killers par excellance. Tyranids can provide incredible bubblewrap and strong melee support, but suffer at range, especially against tanks. Combined, the Tau benefit from the Tyranid's cheap and easy protection and the Tyranids free up their Elite slot to handle other things while not being crippled against mechanized lists. Biovores also add some ability to punish disembarked troops, deep strikers, and anything that tries to hide out of LOS.
1 Tervigon (Cluster, Catalyst, Talons)
5 Ymgarl Genestealers
5 Ymgarl Genestealers
10 Termagants
10 Termagants
1 Tervigon (Cluster, Catalyst, Adrenal, Toxin)
1 Tervigon (Cluster, Catalyst, Adrenal, Toxin)
1 Biovore
1 Biovore
1 Shas'el (MP, PR, MT)
2 Crisis (MP, PR, MT)
6 FWs
10 Kroot (2 Hounds)
8 Pathfinders (Devilfish w/DP)
2 Broadsides (ASS)
2 Broadsides (ASS)
2 Broadsides (ASS)
Orks/Blood Angels: Normally, Orks have a lot of issues; they can't crack tanks well, they die to stuff with decent numbers of attacks due to No Retreat, Side Armor 12 makes Battlewagons often awkward, etc. However, for all that they still have a lot of strengths, and by adding in BA, we can cover most of them. Melta and FNP add immensely to the army
1 Big Mek (KFF)
5 Lootas
19 Boyz (Big Shoota, Nob, Klaw, Bosspole)
20 Boyz (Nob, Klaw, Bosspole)
20 Boyz (Nob, Klaw, Bosspole)
1 Battlewagon (Deffrolla, Big Shoota, RPJ)
1 Battlewagon (Deffrolla, Big Shoota, RPJ)
1 Battlewagon (Deffrolla, Big Shoota, RPJ)
1 Librarian (Sword, Lance)
3 Sanguinary Priest
5 ASM (Melta, Infernus, HF Razor)
5 ASM (Melta, Infernus, LasPlas Razor)
5 ASM (Melta, LasPlas Razor)
5 Devs (4 Missile)
5 Devs (4 Missile)
Permutations
Of course, there are many ways to play doubles tournaments. Quite a few of them simply have each player be separate, with teams friendly to each other and sharing a turn, but otherwise not being able to pass out auras, etc. Doing so means many of the above armies aren't particularly viable, since they cannot share abilities, but on the other hand this opens the field more to non-BA forces.
In this style of doubles tournament, synergy, rather than specific abilities, becomes more important. Codices that cover each other's strengths and weaknesses are of the highest importance and will likely do best, similar to the way the IG/Tau and Tau/Tyranid lists above function. (BA/GK, GW/SW, and BA/SW are still good choices because of similar goals and strategies, but there is less need to focus on the FNP aura and more options to work different units in.)
Another possibility is alternate FoC charts, though this is probably the least common alteration. Some tournaments will make both players use the same FoC, at which point finding codices that have different "important" slots is going to be key. (For example, SW will mesh poorly with anything that relies on its own HS slot, like DE; BA will clash with anything else that makes extensive use of Troops, etc.) This can be an interesting limitation to try and work around, but often ends up being extremely annoying, especially if both players haven't planned extensively in advance for the event. A less restrictive version will usually give each player a downsized FoC chart (something like one four troops and one each of HQ, FA, EL, and HS) and then a number of "free" slots that can be distributed between the team members to whichever selections are desired.
Wrapup
Doubles tournaments can be a fun change of pace from the norm, but at the end of the day they should mostly be relegated to that- something to break up the usual routine, rather than a regular event, since there are some pretty major imbalances in the system as a whole no matter which variation you use. However, as an experiment in optimizing I think they can be a lot of fun, and that's something that shouldn't be discounted.
