My friend and I are debating which game featured it first. My thought was Killzone 2. Then Crysis 2 had it. But my friend says that the feature was implemented in older PC games. However he doesn't remember which one.
http://en.wikipedia.org/wiki/Cover_system first game i played with a real cover system was soldier of fortune time crisis was the first game i played with a cover system... but thats a rail shooter so i wont count it
Been leaning since Medal of Honor: Allied Assault personally at least. On a slightly different note, Medal of Honor: Airborne has hands down the best cover system in a FPS without forcing you to third person.
People have been taking cover behind stuff in fist person shooters since at least Quake, but as far as it actually being a mechanic (like press a button to auto-stick to cover), isn't that more of a third person shooter thing?
Many of you guys are confusing lean/peak with basic cover systems. Rainbow Six Vegas and Killzone 2/3 do NOT have lean/peak systems, they have cover systems that let you aim around or over cover.
True lean/peak systems let you lean around dynamically, and they're OLD. The most recent game I've played that has it are the Medal of Honor games, which have always had the feature. The older Rainbow Six games have also had it too, as well as SOCOM, before both series traded leaning in for snap-cover systems.
The very first FPS I remember playing that had leaning was GoldenEye 64, but I know there were games before it had did it as well.