Goblins are diminutive Greenskins. Though they are arguably the most intelligent of the Orkoid species, they are small, weak, and vulnerabe, and have a reputation for being both cowardly and less than trustworthy.
In Blood Bowl, Goblin teams owe most of their allure to potential and luck rather than actual skill. While they are decent catchers, they are not particularly good at throwing, and tend to get smashed around a lot by the bigger teams.
Goblin teams are most famous among the professional Blood Bowl teams for "dirty plays" - tricks, bribes, fouls, secret weapons - they have all of them in spades. Goblins justify this by pointing out that it helps to "even the playing field."
Historically, Goblins have been viewed as one of the worst teams in Blood Bowl. In fact, Blood Bowl fluff has called them -the- worst team in Blood Bowl on more than one occasion. However, that has changed with recent editions of the game. Whether the Goblins have got better, or everyone else has got quite a bit worse, well, that's up to the individual player to decide.
Goblins are rated as an Advanced Team.
Play Style and Tactics
Goblins have more access to "secret weapons" than any other team in the game, and much of the Goblin coach's strategy must develop based upon when, where, and even if these weapons are to be deployed. Because Bombardiers, Looneys, and Fanatics are classed as carrying "Secret Weapons" it is highly likely that these players will be sent off from a game, sometimes after playing for only a very brief period of time. It is not that a standard Goblin team can't win at all without the aid of such weapons, but they're a huge help. Otherwise, it might be argued they're simply slightly faster Halflings with green skin...
One benefit for the current Goblin team is that the Pogoer is no longer considered to be a Secret Weapon. What's that mean? It means that the Pogoer can't be sent off for using his pogo stick, and a Pogoer can be a tremendous asset to a Goblin coach who knows how to properly utilize him. That said, there is only one such player, and he should be protected with due dilligence, because opposing teams can and will mark him. You have noone to blame but yourself if you do something stupid and fail an attempt to foul with him, thus losing him for the rest of the game.
The two Trolls are very useful to their tiny team-mates, but they can be unreliable, and do have a tendency to eat their friends on occasion.
In terms of play style, Goblins are most certainly an Agility team.
Famous Goblin Teams
The Lowdown Rats are arguably the most famous Goblin team in the Blood Bowl setting.
Games Workshop manufactures an official Goblin Team, including individual figures and a team boxed set. However, because the boxed team was assembled for a previous edition of the game, it lacks the players required to represent the Bombardier, Looney, Fanatic, and Pogoer. These can be found in the Star Players range. So long as you make clear that they aren't Star Players, but simply Goblins using secret weapons, using them shouldn't be a problem.