As much as other people recommend EMG, I have to put Dimarzio in there. EMG will give you more power, and of course that active boost the the bass and treble ranges I'm sure, but I've always found a good pickup from Dimarzio to deliver a better (as opposed to just louder) tone.
And even if having a really hot pickup is your goal, Dimarzio's Super Distortion, Super 2, Super 3, Evolution bridge, Tone Zone, and now especially the X2N (their highest output pickup) is a real monster.
And if you want an artist endorsement. I mean crap.. pretty much every great shredder has used Dimarzio pickups at some time (and usually for a while).
http://www.dimarzio.com
