Ian Paice.
For starters, he plays in one of my favorite bands, so the music he makes is amazing.
Secondly, he is a fantastic player. He's often referred to as the Buddy Rich of rock, and for good reason. He's got amazing chops, both with speed, and precision, and he's got mad groove. I think Bonham outclasses him a little bit on groove (since they were contemporaries) but not by much.
Check out You Fool No One, Burn, The Mule, and Stormbringer for some awesome tracks.