This is really hard for me, as there are tons of rock bands that I love but I'll give it shot in no particular order:
Beatles = I will listen to their music forever. I was humming "Dear Prudence" while getting ready for work this morning.
Jimi Hendrix Experience = The master -nuff said
Pink Floyd -The Floyd, gotta love em!
David Lindley and El Ray-X =Not really and truly rock, kinda hard to define, but Mr. Dave rules.
Wilco - More alt. country than rock, but they can rock out when they want to. I love Jeff Tweedy & Co.
Beach Boys - Timeless harmonies, incredible arrangements, thanks to Brian.
Neil Young & Crazy Horse -Neil Young can rock out with the best of em.
Allman Brothers - Duane, Greg, Dicky, Berry and two drummers. Southern fried Rock & Roll at it's finest.
Little Feat - "I miss Lowell George more than I miss being 8 years old" -Bonnie Rait -ditto for me. Rock, New Orleans boogie, soulful grooves and Lowells' slinky slide work. It doesn't get any better.
The Clash =r.i.p. Joe Strummer. Honest, from the heart rock & roll.