Jimi Hendrix - Voodoo Chile, Purple Haze, Foxy Lady... all good choices that the crowd will (should) recognize.
Stevie Ray Vaughan - Mary Had a Little Lamb (I love it), Tin Pan Alley, Texas Flood... Good blues guitar songs with great guitar work
Maybe Try something in the lines of some classic Black Sabbath????
If you're going for the entertainment factor make sure you do a song that will be recognizable by most of the crowd... that way they get into it... otherwise you'll lose them pretty quickly. Its hard to think of good classic rock songs that would be instantly recognizable that don't have an instantly recognizable vocalist to go along with them... Led Zep, Ac/Dc, The Stones... etc.
