Melee

Melee: The act of using your weapon as a bludgeon. This can be executed by default by pressing the B button on the Xbox version or the F key on the PC version. Melee attacks are both stealthy and save ammo. One melee attack from behind will kill most enemies, provided you can sneak up behind them. This is called an assassination. If an enemy is hit from the side or front, it may take two or three hits to take them down, depending on which weapon is being used. AI's, such as Elites, Hunters and Combat Forms, will melee if you get too close, but they will almost never attempt a stealth melee. A melee is mostly used when an opponent is too close to effectively shoot, to attempt assassinations, if the person is wielding an Energy Sword, and if the user is low or out of ammunition. Assassinating an opponent gives an Assassin Medal, while simply beating them down yields a Beat Down Medal.

Trivia

 * A quick way to save ammo in campaign is to go around meleeing people. It doesn't take very long to kill even a Brute.
 * Hunters will sometimes use their shields as melee weapons.
 * Some fans have called using melee attacks "whacking", and in campaign, when using the method mentioned above (going around in campaign hitting enemies) "Whack-Attack" or "Ammo-Saver-fest '07".
 * Melees are almost useless against Flood Combat forms except when you have its arm blown off.