Just happened by this thread on a google search. But anyway, I have a Real Rhapsody subscription, and all I've been doing for the past couple of months is listening to every instrumental rock/metal/guitar album they have. These are the best I have found--and I've listened to hundreds. A lot of them are obscure. Some are done with drum machines instead of full bands, but they still sound awesome.
Band Name--Album--Tracks
Spiritus Mundi--Trinity--Circle of Seven/Dead in the Water/and almost all the others.
This album kicks so much *****, I can't even tell you. Crunchy, heavy guitar riffs. Like Metallica without singing. The Circle of Seven song is 17 minutes and it's so freaking good. Done by one guy, I believe--a genius.
Theodore Ziras--Hyperpyrexia--Number One/Salvation/Night of the Dead
Speed metal guitarist from Greece. Blinding solos, heavy riffs. You get the idea. Really good.
Corbin King--Guitar Master--Blue Groove/8th Degree/some others
Another speed freak guitarist. Unbelievable technique and speed and tone. Lots of heavy stuff, some bluesy. But the guitar wails, man. Also check out his other album Destination. Him, Joe Stump, and Michael Harris all released separate albums playing the same songs to see how they interpret them. It's awesome. Joe Stump's album is called Armed and Ready, Michael Harris's is called Hurricane X. But they all play the same instrumental songs to see the difference in technique. It's pretty sick. Joe Stump on the track Mind Games is some of the best guitar playing ever.
Michael Harris--Orchestrate--Octavian II
I'm not recommending the whole album (some of the songs are good, though), but this one track is a must own. One of the best metal instrumentals I've heard. It's not recorded in the best quality ever--drums are a little thin--but the melodies and the guitar playing make up for it.
David Chastain--Countdown to Infinity--Title Track/Demonic Harmonic.../Attack of the Mechonrites
More must own tracks. These are just as good as all the others. Wil definitely have you banging your head and looking for trouble. The title track is serious head banging.
All of Joe Stumps stuff is insane. He is the most underrated guitarist in the world--unblievable skill. Tracks Mind Games, Jetaime, and Sorcerer's Apprentice are good.
Jeff Kollmann--Schizoid--Remember the Alamo/Detroit Monster Blues
Not recommending the whole album, but these tracks are really good. Amazing guitar playing.
Nick Layton--Storming the Castle--Snake Charmer
Amazing song. Great heavy riff, Clean speed guitar. A couple of the other songs are good, but this one stands out.
Check out Jeff Loomis's Zero Order Phase if you like that real heavy stuff. There's a lot of others. Oh yeah there's a song by Keith Miller called Inner Turbulance on his CHALK album. Awesome song. Great melody, heavy riff, clean guitar with nice tone.
This is just the metal/borderline metal stuff. If you like instrumental blues/rock guitar I have tons of awesome obscure tracks.