You want something with a high output but with some good definition too.
The DiMarzio Evolution is a good choice. I have one in the bridge position of an Ibanez and it definitely chugs. Also the PRS HFS is a really fat high output pickup. Also, EMG pickups rock for heavy stuff. I believe the 81 is their super high gain pickup. You can also get the EMG Zakk Wylde pickup set (I think it requires that you have holes for 2 volume controls and 2 tone controls like on a Les Paul).
You might also check out the Seymour Duncan website. It has detailed sonic descriptions of all their pickups.
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"You never can vouch for your own consciousness." - Norman Mailer
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