Going to focus on FPS's for a moment here... Lets take a look at the ones that try to be "realistic". I'm looking at you, every army based shooter game ever made, especially all of the WW2 ones, but more importantly the team based online ones without the HP bars.
"Pinning down" as has been previously mentioned CAN be done! It's a defensive tactic that I use alot, where you simply shoot bullets in logical locations where you think enemies are. I've had this used against me too, and it's frightening when you're really into the game, because you don't know where it's safe to poke your head out without getting it shot... So you wait for somebody to flank them, or look for an escape. That's pinning down. UNFORTUNATELY, there are two problems with "realistic" shooter games, these being the unpredictability of players whom know they can just respawn when killed (way too many suicide charges) and the unrealistic degree of accuracy obtained by having a crosshair on the screen, that can turn ME (a coward with shakey hands) into a sniper with regular rifles with very little practice.
But of course, they'll never be convincingly realistic until my pistol can kill a dude in less then 5 shots. Yes I know it's a dinky little pistol, but it still shoots bullets! I'm really sick of every FPS ever made only rewarding people for overcompensating (if you catch my drift) >=/
TF2 on the other hand, is my favorate FPS at the moment. Why? Because I hate wetting myself every time anybody shoots at me with anything bigger then a pistol! I have HP, I can take a round or two, and if things go bad I can retreat for healing, and chances are the time taken to heal will not be wasted as I'm 1-hit-KOd by my next encounter! (which also ruins realistic gaming, by further removing any reason to care about your own mortality) And also, I like how I can actually kill people with MY pistol, without any noticeable loss of efficiency vs the bigger weapons.
Flexible games ftw.