I don't think I could ever pick just one.
In my high school days, I would have jumped off of a cliff to be Vinnie Paul, but that was then...
I would say my faves are (in no particular order):
Neil Peart
Carter Beauford
Buddy Rich
Danny Carey
Sammy Watson (apex theory)
Vinnie Colaiuta
I don't listen to Dream Theater, but good God I could watch Mike Portney play all by himself all day...