Orcs and Goblins are one of the most popular armies in Warhammer Fantasy Battles, and rightly so: even with their old book they were an army that could be built in a ton of different ways. Even better, with their 8th Edition book they lost none of their versatility and gained a healthy dose of competitiveness.
When I say that the book is two armies in one, I am actually referring to the Orcs and the Goblins. While you can (and should) mix units from the greenskin cousin, each side of the very green coin has it’s own flavor and feel. You could be a Goblin fan and make several armies that never even consider Orcs. This is more or less unheard of in 40k; the only army that comes close is Grey Knights where you could bring an entire list of power armored GK or a list entirely composed of Inquisitorial units. Orcs and Goblins go far beyond that, though.
Within this duality, there is even more variety. Whereas, say, Dwarves are a shooty force of infantry with warmachines, Orcs and Goblins can be built in tons of different (and competitive!) ways. Do not consider the following list to be an exhaustive survey of the different types of armies you can make with Orcs and Goblins, but merely a starting point to pique your interest.
First and foremost, we think of the greenskins as a horde force. Orcs and Goblins can field very large infantry forces that are only outsized by Skaven and Vampires. Honestly, I do not believe that going ‘all-in’ on an infantry horde is very competitive, as the magic and shooting phases severely punish such an approach to victory. Large infantry blocks have a place in most OnG lists, but an army composed solely of them is not set up for great success
Chariots! I love chariots in Fantasy, I feel the buffs they got in 8th Edition have made them one the premier offensive units in the game. Orcs and Goblins can do chariot spam better than almost anybody, in that they can bring more chariots than anybody. As any seasoned players knows, a Strength 4 impact hit is a Strength 4 impact hit, regardless of the race of the charioteer. Impact hits are extremely brutal, and the best way to get more of them is to bring more chariots. This army is composed of lots of Orc chariots, backed up by even more Goblin Chariots, backed up by characters backed up by warmachines. You see, chariots are exceptionally good at killing MSU elite units, but can get tarpitted by large blocks. Thus, you back up your chariots with warmachines designed to kill large blocks. By covering all your bases in that way, you achieve army balance.
So maybe chariots aren’t your style. Maybe you prefer more traditional balanced approach. Orcs and Goblins have you covered. As they possess some of the most cost efficient infantry in the game (Night Goblins and Savage Orcs) you can tailor this approach to your theme or preferences. Start by filing your core choices with Savage Orcs and/or Night Goblins (with Fanatics) until you have a healthy amount. Add a Black Orc battle standard bearer to keep your leadership steady. Add a Level4 Goblin Night Goblin Shaman and a handful of Level2 Night Goblin Shamans. Goblin magic is two fold superior to Orc magic: they have lots of power dice to cast spells and their spells are great at influencing combats in your favor. Since resolving combats in your favor is how you plan to win, this is the way to go. You’ll back this whole force up with goblin chariots or wolf riders on the flanks, and a balanced array of warmachines. This is an army that has a little of everything and does it all very well, which you might not expect from Orcs and Goblins.
Orcs and Goblins are also very capable of running a Monster Mash list. Their characters are relatively cheap, and many of them can be given monstrous mounts. Combine a Goblin Shaman on an Araknarok Spider and another in the Rare slot, along with Mangler Squiqs, chariots in the core, and as many characters as you can afford riding monsters and you have a list of heavy hitters. This may not be the absolute most competitive lists, but if you play Fantasy because you drool over the huge centerpiece units, this is a list full of them.
The last playstyle I’d like to mention is the Orc Gunline. Believe it or not, but bringing the maximum number of warmachines (especially Goblin Spear Chukkas and Doom Divers) with a core of Arrer Boys backed up by magic can be quite effective. If rolling tons and tons of dice and destroying your opponent with a hail storm of arrows is your idea of fun, this is the list for you. It’s unconventional to be sure, but no less effective. Most people will not be prepared mentally for an Orc list that can shoot them off the table. Coincidentally, this is the list where you want to use Orc magic over Goblin magic, since Orc magic is pretty good at smashing opposing units: Foot of Gork is rather effective at killing, well, everything.
There are at least half a dozen strong builds you can make out of this army book, and the ones I talked about are just scratching the surface of the possibilities. I feel I should also point out that the fluff potential for theme armies is also very high in this book. You could make a Black Orc themed list, Savage Orc tribal list, a Night Goblin list. Heck, I’ve heard of people playing a Spider themed Goblin army. Assuming you are a fan of the mean greenies, there is something for you in this book.