In Deus Ex: Human Revolution for the PC, PS3, and Xbox 360, you can melee enemies close up to perform a takedown, which nets you a lot more XP than simply killing them with a weapon.
You can’t simply punch like in other first person shooters however, it’s more of an action, and requires a bar of energy.
In order to melee someone (aka, perform a takedown), you need to get close enough to them and press the action button for it that pops up on the screen. On Xbox 360 you press the B button, and on PS3 you press the Circle button.
This can be done even when an enemy is hostile, and the animation will be different depending on where you’re located near the enemy. For example, facing an enemy can trigger the face punch animation, while doing the action from behind the enemy can trigger the choke hold animation, or a nice tap on the shoulder followed up by a hay-maker to the face.
You can perform takedowns on regular citizens as well, even if the option doesn’t show up on the screen, simply press the right button in range. Don’t be alarmed if this makes nearby police hostile toward you though.
It is kind of gratifying to punch a Punk in the face when he starts talking smack though.. just saying.
