Nitro. I don't know what it is about those balls, but they are long for me.
My favorite ball is a ProV; they just feel good off the club and I get good performance from them. But they're too expensive for me to play. I like Titleist Velocity, too.
I basically play the balls that I can get the best deal on. I usually play the black Callaway's from Costco, but I scored a bunch of Taylor Made Jetspeeds at $10/doz at Canadian Tire, so I've been playing those, too.