We'll start with a Seymour Duncan JB. It's a great pickup for one particular reason. It's the most sold Duncan pickup, so there's a lot avalible on the market. What's funny is all the negative comments I hear about it. I've never heard a pickup called both muddy by some, and too thin by others. I'm not crazy about them since I find them too compressed.
However, there is a way to take care of that, and get an awesome pickup out of an average one. Namely, replacing the Alnico 5 magnet with an Alnico 8 magnet.
Here's a picture of the pickup, an Alnico 8 magnet, and a compass:
First I undo the four screws on the bottom:
You may have to push on the back side of the magnet, and/or grab the front with tiny tools. I did both. Either way, get it to slide out like a stick of gum.
It is loud. This is a pickup that you don't have to put too close to the strings since it is so fire-breathing hot. But unlike a lot of hot pickups it is pretty open sounding due to the lack of compression.