If a humbucker has the 4 conductor wiring, you can rewire it in parallel rather than series (typical humbucker wiring). Wiring in parallel will cut the output almost in half, as well as affecting the tone by cutting some of the bass and low-mids. It will give the humbucker slightly more of a single coil sound, while still being hum-canceling...

If you are interested in learning more, here is a good site that explains it pretty well: http://www.1728.com/guitar.htm
Go about halfway down the page under 'Humbuckers'.

I recently rewired a humbucker to parallel, but I ended up switching it back because I liked the fuller humbucker sound. Ideally, putting a switch in so you had a choice between series or parallel wiring would be the best way to go. It would be like having two completely different pickups in the guitar...