First and foremost, Rush. Alex Lifeson's playing and tone on All The World's A Stage completely rewired my perception of rock guitar. It's really still my reference point to this day, and informed my actual playing much more than any other band/guitar player.
Beyond that, I figure everything you hear influences you a bit, whether you realize it or not, but the big obvious ones for me are:
Black Sabbath
Judas Priest
ZZ Top
Aerosmith
Led Zeppelin
Yes
Lynyrd Skynyrd
Bad Company
The Beatles
UFO
Scorpions
Kiss