Tool: I should probably like this band, but I find the music just too... bleak and depressing to listen to. I used to work with a guy that would play Tool all the time at work and all the music just flowed together into one oppressive whole, nothing really stood out to me. I do like a few of their songs (Vicarious, Third Eye, a few others), but I just can't get into their music.
Radiohead: Thom York has an irritating voice.
Judas Priest: I appreciate their role in the formation of heavy metal, but compared to contemporaries like Black Sabbath and Maiden, I just find them to be lacking in something.
Spock's Beard: I enjoy X, their self-titled, and The Light, but they're too cheesy for me to appreciate their entire catalog.
Protest the Hero: Excellent musicmanship, but every song sounds like 3,000 ideas squashed together into a cacophony of music with no melody. Some may enjoy this, I find it tiring and, after a while, boring.