Melee

As shown by bungie.net
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 kill them, 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.

Character compability

• Spartans
• Elites
• Hunters
• Brutes
• Marines (only if a jackal or grunt gets too close. Also, can melee an Elite from behind)
• Flood Combat forms
• Flood Pure Forms

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 (with a Brute Shot).
• Hunters will sometimes use their shields as melee weapons.
• Some fans have called using melee attacks "whacking" and "Nutting", 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. However, in Halo 3, the melee is actually more powerful to them. A newly infected Combat form will usually die with 1 blow while and old combat form should die in 2-3 blows.
• In Halo 2 multiplayer, it can take up to six melee strikes to the front or side to kill a fully regularly shielded enemy. In Halo 3 multiplayer, if the target has no Overshield, only two strikes to the front or side are needed.
• In Halo 2 and Halo 3 the melee attack has a small lunge distance.
• It seems in Halo 3, melee attack are moderately more powerful than it was in the previous Halo games. This allows players to combat enemies with ease, also the reason why Flood are weaker to melee attacks in H3 may be due to this powerful "Whack-Spaunk" bash-up attack.
• In the recent update to Halo 3 the Melee attacks are more balanced and if there is any doubt then both players die and get kills.