Going waaaay out....
Old swing/jazz: Benny Goodman. Maybe it is because he was my mom's favorite musician. Besides his talent, and all those who were part of his ensembles (Gene Krupa, anyone?), I have learned of what a 'revolutionary' he was. I will often listen to his music, and think of how well a RnR lead guitar would fit in.
Blues: Stevie Ray Vaughn. Occasionally, I'll play a B.B. King or Joe Bonamassa track (his cover of Zep's 'Since I've Been Loving You' is amazing). For all of the talented artists and musicianship, I just cannot listen to any other blues for more than a song or two. Attended a couple of all day festivals decades ago, and wasn't sure whether to continue drinking too much beer, or slashing my wrists
Hair/glitter: Motley Crue. Their 'best ofs' up through the entire 'Dr. Feelgood' album are listened to often. Can't stand GnR, Poison, Cinderella, etc.
Grunge: Soundgarden, Pearl Jam, and some of Nirvana. No, I didn't listen to a lot of their work, but I did not hate it as I did all the others. The problem was the overplaying on the airwaves of Nirvana. I could listen to their 'Unplugged' on a weekly basis, though.
Alternative: REM, though I preferred their heavier stuff, and totally gave up on them when Billy Berry left (though their last two LPs harkened back to their glory days)
Mellow: Not into all of the soft and cheese, but Carole King's 'Tapestry' and Dan Fogelberg's 'Netherlands' and 'Phoenix' get heavy early morning/late night listens.
Crooners: Frank and Tony, nothing else. Have come to really appreciate their talents over the past decade. Sinatra's 'In The Wee Small Hours' is often credited as being the first concept album. Bennett....at frickin' 90, he still has the pipes!!!!
Whatever category Dream Theater fits into: not a fan of Iron Maiden (thought respected), Opeth, Trivium, Between The Buried And Me, Mastodon, Epica, etc...