I'm surprised no one has mentioned Conti GP4000 yet. The other tire thread going on right now, that was 80% of everyone's choice.

I'm on my third front and fourth rear and just love them. They've got a nice round profile that gives my bike great handling (as opposed to the Michelins with their built-in flat spot - Michelins came on my bike and the difference was amazing when I changed them). I rarely flat (touch wood). I get about 2200+ miles out of a front and 3500+ rear, and I usually replace them before they're all the way down to the wear indicators. Plus they come in purty colors (in 23c, the 25c tires are black only).