If I have to pick one I'm going with Tool. They were my soundtrack from basically 1995-2005. My musical tasted have drifted and expanded as I've gotten older so I don't listen to them nearly as much as I used to, but no other band has had so big an impact on my life. Aenima and Lateralus are still two of the few albums where I can listen to the whole thing in its entirety.
YES! Since I first heard Prison Sex (the song, not the sex) many years ago, I fell in love with them. Been a bigfan since. Was lucky enough to see them a couple of times over the last decade and a half.
Lucky! I was only able to see Maynard once in 2000 when he and A Perfect Circle headlined for Nine Inch Nails.