I watch quite a few, actually.
MadameWario (thanks to SlimKirby)
Carl1o01, BoogyMushroom/BoogyTroy, and their combined playthrough channel BoogyCarl.
Since nobody's mentioned those two yet... Carl is playing Super Mario Sunshine (Getting the blue coins by now) Majora's Mask, and Half-Life 2, I think. Booty is working on Earthbound and maybe something else, I don't know. Together they're playing Mario Party 5 and Halo.
MadameWario is LP-ing Paper Mario and Super Mario Kart.