I'm going to say the wooden staff from Dark Messiah. It only does damage even comparable to any blade when you're using the force strike, and that's a 3 hit combo that most enemies can easily dodge and you can't move while doing it. A melee weapon in which the most only powerful attack is basically crippling you just long enough for any blackguard or orc to run up to you and stick their rusty swords up your butt.
Oh, and while we're on the subject of Worms: the cluster bomb.
Oh, and while we're on the subject of Worms: the cluster bomb.