IIRC Vietcong 1 pulls it off pretty perfectly, at least I never seen it done better. Extra bonus point for a semi intelligent, simple routine, that determines dynamically wether your run/walk and crouch buttons are to be treated as toggles or switches. Click once to toggle, keep pressed to perform action until you release button, no useless hassling with the options/keymaps.
IIRC GRAW2 (didnay play 1) makes em lean adaptively out of cover a bit. At least you CAN lean, which actually is enough to make use of cover. Since popping your head out OVER a cover actually isnt that much of a good idea. (you need to expose more of your body to be able to shoot when you pop out over, also those parts tend to react more critical to injury. I mean, I rather not get into a firefight, but if I had to, and I got hit, I'd rather have it in the shoulder than in the brain, please
)
Graphics might be dated, but if you think you're interested in something like this DEFINETLY try VC1 (2 wasnt that good...), you can even consider buying the purple haze edition, which includes the expansion pack, iirc. Should be cheap, imho definetly worth it.
Devs played a lot of woodball before they went to make that game, and imho you notice that, in a positive way.