I really like the one sebi40 uploaded. Why aren't there more such scenarios with live models? Personally I'd love to see one with redhead pornstar NIkki Rhodes slamming a glove into her opponent's nuts.
Related to this idea is this, in which the woman doesn't actually take part in the fight, but goads two guys into busting each other, saying the winner gets her. (If you've been to bars, you know there are women who love to do this kind of thing -- get two horny guys boiling with lust to fight over her.) Have a look: