There's plenty of them of course, but here's some of the ones that impacted my guitar playings.
1- Stevie Ray Vaughan

His unique way of playing the blues made me open my eyes wide.
Another reason for liking him? He uses the same guitar as i do. Hehehehehe.
2- Slash

Huh? If Slash doesn't inspire anyone about guitar, it's time to start playing another instrument. I started playing solos by listening to him. And practising around 2-3 hours a day. Yes i am crazy.
3- Zakk Wylde

His style and technique. That's all i've gotta say.
The bloody guitar squeal. The riffs. The muscles. The beard. (hehe)
and last but not least...
4- Kirk Hammett

My favourite guitarist.
Thought me speed and skill for my fingers.
I learned most of the guitar stuff i play from watching him play.
I'm a happy man now.
When i talk about guitar stuff, i smile.
Hehe. Smiling is just what i need right now.
:)