Mine is the Liberty Bomb because it goes "halleluja" and blows up.

its called the holy hand grenade

I once did a four person multiplayer where there was just one small piece of land, sixteen worms, and lots of exploding barrels and land mines. The first worm to move detonated the enire screen. The match lasted one second.

After that, Old woman is my favorite weapon, followed closely by sheep. Poke is good, too.

p.s. the match above ended in a draw.