Lord Undies & Freedumb Know of what they talk. Dukenukem shows potential. Rest y'all should hang your heads in Shame
added edit: I just looked back that only left Chris,what's the problem dude. 
I know there are more but the only band I can think of for sure that needed to never happen is Depoche Mode (commonly referred to as The Puke Mode )
all Modern day rock owes their existance to Deep Purple, Black Sabboth and perhaps Judas Priest.
I actually met Hootie and the Blowfish once, in a way it was like that Beach Boys episode of Full House.
They came into this bar I was in, the bar tender got all excited because he was a guitar player in a band or something kids did in those days and one of the guys, the red haired one, came up to the bar and I ask, "oh, so you guys are a band?" and he said "yeah" somewhat defensively and so I asked which one and he said "Hootie and the Blowfish" and I said, "Oh, I've heard of you guys" which was true, but I had never heard their music at that time.
Back in those days, I mostly listened to NIN and Nirvana and such.
So, Hootie made my list because if they never existed then maybe NIN or Sound Garden or some hot chick band would have come into the bar and I would have a better story.
Curse them! They're the whole reason why I'm not having grandchildren.