Drums and percussion.
Neil Peart - Rush, one of the best.
Dave Lombardo - ex Slayer, tremendous.
Tommy Lee - Motley Crue.
Joey Jordison and the other guys from Slipknot are awesome too.
Too many more to mention.
Another vote for drums...
Dave Weckl - Chick Corea Electrik Band and The Dave Weckl Band
Dennis Chambers - numerous fusion bands.
Steve Smith - Journey and Vital Information
David Garibaldi - Tower of Power
Steve Gadd - Steely Dan and much more ...
Coming from a drummer, I'd have to say drums, Derek Roddy, Buddy Rich, Paul Mazurkiewicz and John Longstreth are some of my favorite. But guitar is a damn close second. I'm a huge Steve Vai fan.
Since I am a percussionist my first love and respect goes to percussionists and drummers the players that come sprining to mind first are....
Artis The Spoonman - Spoons, Bones, Ladles
Rónán Ó Snodaigh - Bodhran/Percussion for Kíla
Gino Lupari - Bodhran/Percussion for Four Men and A Dog
Future Man (RoyEl Wooten) - Drums/Percussion for Bela Fleck & The Flacktones
Tim Alexander - Drums/Percussion for Primus, Laundry, Pucifer, Attention Deficit, Et Al.
Mike Dillon - Percussionist for Col. Claypools Flying Frog Brigade
But I halso have a not so secret affection for amazing Bass Players, My all time favorites are:
Les Claypool - Soloist and Primus, Sausage, Oysterhead, Col. Claypools Flying Frog Brigade, C2B3, Electric Apricot, Et. Al.
Victor Wooten - Soloist and Bela Fleck and the Flecktones
Edgar Myer - virtuoso double bassist.