Van Halen's first album... great to jam to cause you can turn the balance to one speaker and get just the drums and bass. Same thing with a lot of early Beatles stuff.
City Boy is an amazing guitar band too with great harmonies. The song 'Cigarettes' is one of those classics with some great riffs.
Rush 'Hemishperes' or 2112 are kinda groovy.

...and some other bands I'd be suprised if anybody's even heard of...
Chilliwack, Brand X, The Box, Dixie Dregs, Harlequin, King Crimson, Missing Persons, Uzeb, The Tubes, Sweet. XTC.