Ok, I've got a couple of older ones. This might upset some people, so I apologize in advance.
Bob Dylan. I'm told that he's the greatest poet who has ever lived, but let's be honest. The man can't sing. I'm sorry. I really am, but when the only chance you've got of hitting a note is to slide all over the scale, that's not singing. When the audience has to work harder to understand you than you had to work spitting out the words, it's just not worth the effort. Sorry.
Neil Young. I know I just crossed a line with this one. He's got a voice that sounds like a cat being pulled across a cheese grater. I would say that I hate it, but that term may not be strong enough. Also, I prefer guitar solos that utilize more than one note.
Right now, someone's staring at their monitor with their mouth hanging open and their fists clenched in rage. I'm sorry for that.