Goblin Fanatics are 3 foot high drugged-up green-skinned nutters from Games Workshop's Warhammer games.
Fanatics are used as living weapons by the night goblin tribes who keep them tied up nice and tight and feed them all manner of psychoactive and strength-enhancing fungi. When they are used on the Blood Bowl pitch (think american football with orcs), the fungi are brewed into potent beer. Whatever, the net effect is to turn the short chap into a frothing, incredibly strong, absolutely fearless and completely berserk lunatic. The fanatic is tied up until the Goblins get near to the enemy, at which point he is given a huge ball & chain, easily weighing twice as much as he does. The fanatic spins the weapon wildly, vaguely in the direction of the enemy. The effects of a successful attack are devastating, scattering units in a panic and crushing armour and bone with equal ease. Of course, their somewhat unpredictable nature means that quite often the Goblins suffer as much damage from a fanatic as their enemies, but the psychological effects make the risk woeth taking. That, and the fact that Goblins are quite stupid.
Sadly, Goblin fanatics tend to be rather short-lived, as they are prone to strangling themselves with their own weapon, dying of massive heart failure due to their excessive intake of fungus, or even to being shot by unsporting enemies with bows. This tends not to be a problem for the Goblins, however, as they breed quickly and have no qualms about smacking some other poor Goblin over the head with a big stick and feeding him fungus until he sees the merits of becoming a fanatic.