I am a HUGE fan of AXY FatBoys.
My Custom fretless 5-string has one in the bridge position, and that was my gateway. At some point, I will probably upgrade the neck pickup to match it. While waiting for her trip home to the Wizard's Workbench for new pickups and the RF Upgrade-Plus, my Series I wore a pair of Fatboys for almost a year. Those same 'meant-to-get-me-by' pickups are now installed in a fretless Distillate Custom, instantly expanding it's voice in the same way.
Others have said having both pickups as FatBoys is too much, and in all honesty, I can see how that might be for some. Works for me though.