Like in Stalker where the mutant dogs will turn tail and flee if they take too much damage or if you kill enough of their pack members. Red Dead Redemption's animals also ran away if a fight wasn't going their way.
Actually, Rockstar games are pretty good with this sort of stuff in general. I'm pretty sure you could shoot guns of of people's hands in RDR to make them put their hands up, or cause a fatal gunshot wound that would make them crawl around on their belly and call for help. Both GTA 4 and 5's enemies have injury states where they will take potshots at you with a pistol while bleeding on the ground or just passively clutch their wounds until they die.
I guess it wouldn't work in arcadey or linear games where the point is to kill everything on screen, but for anything more open-ended that tries to go for something approaching realism it'd be nice if the enemies you faced felt more alive and/or showed some basic survival instincts.
My wargame encourages voluntary falling back, but you can fight to the end if you want. It's not good for losses and is pretty ineffective at giving enemies a bloody nose, but it can hold up enemies for up to half a day at a time!
Generally you want to conserve strength and retreat if fatigue gets too high (fatigue being a general measure of a unit's readiness, tiredness, the supply situation etc), but sometimes you gotta hold that bridge or linchpin town