An somewhat accurate and interesting thing about the original Quake is that each time one shoots an enemy (especially soldiers), they stop and shudder, which conveniently gives the player time to finish them off.
Not accurate but useful to the player is that if an enemy is on patrol when you're shooting them one by one as they come around a corner, each enemy cheerfully walks into your field of fire even they have to step over their fallen comrade. Their cluelessness would make you think they work for an Evil Overlord or something.
I would also say the initial reaction time of most enemies needs work; if the player is awake when an enemy appears, one can channel Han Solo and shoot first.
Possibly accurate (ot not) is if the player has a number of enemies (in particular, Ogres) in one spot, and one can get out of the way, they'll attack each other. (Maybe they just don't get along.) In any case, it saves on both ammo and wear 'n tear on you, especially if the last two manage to kill each other at the same time.