Does Brink give you an option to melee an enemy? Ive watched all the videos and seen pictures of characters with knives but I dont think Ive ever actually seen someone melee another in-game.

Is this possible? And if so are they like COD one shots? Does everybody get knives? Do you just punch them, or maybe go halo style on the guy and hit him with your gun?

There is melee but it is not a OHK. Typically knocksdown opponents.

Yeah, you hit the guy with your gun and he gets knocked down.

Pistols let you knife people, and you can either normal melee or slide into an enemy to do physical damage.

There is melee. Gunbutts and slide tackles knock prone. Knife is only with pistol usage.