Neil Peart, closely followed by Cozy Powell. I never saw Powell live sadly but Rainbow Rising and the subsequent Rainbow live albums are awesome.
Peart is in a league of his own, i've seen Rush in concert, i've seen concerts, i heard their music and honestly it's astounding how he sounds likes an octopus with 8 arms when he only has 2 arms and 2 feets. Watching his drum solos is mesmerizing.
In the comments Jeff Porcaro and Phil Collins where mentioned, i think those are the two drummers with such a unique sound that you simply can detect them. A lot of drummers are just drummers and get lost in the mix or are pushed in the background - or work with just one band like neil peart. Collins and Porcaro have such a distinctive style each, you hear them, like I Know There's Something Going On from Frida, you hear the first drum beat and you just know that's Phil Collins. Porcaro has the same on his work with Steely Dan on the Katy Lied or his work with Toto