I'm odd when it comes to games, especially video games. I'm not a console gamer at all; only game console we ever "owned" was a Magnavox Odyssey -- and really, we only had that a week, so maybe we just borrowed it. Didn't have much disposable income to play games in the arcade, and I was slow to get into PC games, usually getting into a particular game after everyone else has moved on to the next shiny thing.
So, I've played video games a lot in the last couple years, but I haven't played a lot of video games. I've mostly stuck to older FPS shooters that don't play like a deathmatch game, something more like a puzzle-style shooter: old Doom, Heretic, Hexen, that sort of thing. I prefer taking my time, trying to avoid dealing with too many monsters at the same time; I treat it very much like a dungeon crawl, listening for sounds of monsters in the next room or looking for traps.
And tricking monsters into killing each other.
It's one of the elements of video games I'd like to see more of in tabletop RPGs. The general rule is usually that monsters of the same type can't accidentally hurt each other, but those of different types can, and they get ticked off at each other as a result.
This could be pretty easy to do in D&D with just a morale roll every time one kind of monster accidentally injures a different kind. The chance of turning on each other is based on either the mutual feeling of the two groups or on the loyalty to the leader, if present. For example, if a leader is present and the loyalty is high, any reaction roll of high or below prevents the groups from turning on each other; a very high result means a fight breaks out in the ranks.
The default mutual feeling for mixed groups is Neutral. Friendly groups have a high chance of avoiding dissension in the ranks; hostile groups (including different orc tribes) have a low chance of avoiding dissension. You can consider homogenous groups to be Friendly at least, unless the creature type is extremely chaotic, paranoid, or known for internal hostility.