Aquafresh Extreme Clean.
I'm not one for things with the word "extreme" in it but I gotta admit, the AEC lives up to it's name. Excellent foaming action -- with a sonicare brush, most toothpastes just liquify and you don't feel the clean, but with AEC, it still foams up nicely. Very refreshing after a brushing session.
(That was a bit much for a toothpaste post, yeah?)