can't believe thread has lasted 7 pages without any mention of Pete Townshend?!
here's him doing Pinball Wizard solo in the early 80s
YouTube - Pete Townshend-Pinball Wizard - nuff said.
other votes for great rhythm players:
Malcolm Young
Bille Joe Armstrong (stop laughing)
special mention for Tim Armstrong (strangely no relation to billie) - try playing ska grooves on the downstroke... i still can't kena that!
also have to give props to Plain Sunset's Jon Chan, who is by far one of the best rhythm guitarists i have had the pleasure of watching and playing with. i used to think my rhythm was good, but after constantly playing with him for the past 5+ years, this guy totally takes me to school everytime with his crazy tight rhythm groove. AND! he's a pretty sick lead player when he wants to.