Here's my list:
Frank Zappa:
No one gives the man credit for being a simply astonishing, unique guitarist, easily compared to Jimi, Clapton & all the other established "Guitar Gods". For best examples, check out these albums:
"Overnite Sensation"
"One Size Fits All"
"Roxy & Elsewhere"
or just get his 3-CD guitar collection "Shut Up & Play Yer Guitar"
Lowell George:
For my money, the greatest Slide guitarist ever. Tone, feel, economy, all of it perfect.
Phil Manzanera:
of Roxy Music, 801 etc.. - another fantastic "texture" guitarist who can also take a mean lead when the song demands it. Capable of just about any style while always sounding like himself.
Bill Nelson:
of Be-bop Deluxe, and long and largely unknown solo career. This guy is a legitimate "Guitar Hero", but was ill-served by his band being dumped into the "Glam Rock" category of the time, and never taken off in the US. In my opinion, "Axe Victim" is one of the finest "guitar rock" albums of all time, not to mention having the cooooolest cover:
Billy Gibbons:
Behind all that facial hair & fuzzy guitars lurks a first-class blues/rock guitarist. The 1st 4 ZZ Top albums are all examples of the greatness of his playing. For the old record-diggers; check out his pre-zz band, "Moving Sidewalks". Some really fine guitar playing there as well. They opened for Hendrix in '68, and he said of Gibbons "The best damn white guitar player i've ever heard"
Eddie Hazel:
The lead guitarist for Parliament/Funkadelic before his untimely death in 1978. I refer to him as "Jimi's bastard younger brother" 
The original "Maggot Brain" and the inspiration for the song of the same name. The guy was simply a furious guitarist, and his early work with Funkadelic makes me think that it was the direction Jimi was heading in, had he stayed alive.
I'm sure i can dig up more, but those are the ones that immediately come to mind
