One who uses their painful foot deformity (see bunion) for the benefit of sexual practice. The bunionfucker takes advantage of their foots extra protuberance by using it alongside or in replacement of another bodily appendage during sexual intercourse. They may also take advantage of the unsuspecting bed-mate.
Christa: My GAWD those callus covered bumps on your feet are disgusting!
Elton: Yeah, but they do come in handy
Christa: What, how?
Elton: Come with me, I'll... explain...
Christa: Your a bunionfucker aren't you
*stomps on Elton's bunion and walks away*