Halo 3 Multiplayer Medals

Multiplayer medals first appeared in Halo 2, these medals where counted up and shown in the post-game carnage. This is the same for Halo 3. When a player kills another in a way other then a generic way (e.g. Assault Rifle Fire) a medal will appear showing what the player had finally ended the opponent’s life. For example, If a player kills another such as a sniper headshot or a melee then the will be awarded with the corresponding medal in the bottom, left hand corner of the screen.

Multi-Kill Medals
If a player kills a player then kills another within 4 seconds of the preceding kill, then they will receive a Double Kill Medal. There are several more multi-kill medals after this, See list below.
 * Triple Kill
 * Overkill
 * Killtacular
 * Killtrocity
 * Killamanjaro
 * Killtastrophe
 * Killapocalypse
 * Killionaire

Spree Medals
Spree medals are rewarded when the player kills a number of players in a row over any amount of time. The spree is reset when the player is killed. There are also medals for killing several players in a row with different weapons (e.g. Shotgun Spree, Slice ‘n’ Dice) and other medals are given during objective based game (e.g. Flag Stop). Below is a list of the spree medals.

Kill Spree’s

 * Killing Spree
 * Killing Frenzy
 * Running Riot
 * Rampage
 * Untouchable
 * Invincible

Weapon Sprees

 * Shotgun Spree
 * Sword Spree
 * Sniper Spree
 * Splatter Spree
 * Open Season
 * Slice 'N Dice
 * Sharpshooter
 * Vehicular Manslaughter

Objective Spree’s

 * Hail to the King
 * Infection Spree
 * Zombie Killing Spree
 * Juggernaut Spree
 * Mmmm Brains
 * Hell's Janitor
 * Unstoppable

General/Vehicle Related Medals
Some medals require the player to achieve something other then the run of the mill kill.

Special

 * Perfection
 * Extermination

General Medals (Common Medals)

 * Beat Down
 * Assassination
 * Sniper Kill
 * Grenade Stick
 * Laser Kill
 * Oddball Kill
 * Flag Kill
 * Incineration
 * Killjoy
 * Death from the Grave
 * Splatter
 * Highjacker
 * Bulltrue Wheelman
 * Skyjacker

Objective Based Medals
When playing objective based game types such as Capture The Flag, medals are rewarded for actions that contribute to the game, e.g. Killing a player who has you flag will earn you the Flag Stop medal. Below is a list of the objective based medals.
 * Last Man Standing
 * Killed Flag Carrier
 * Flag Score
 * Killed Juggernaut
 * Killed VIP
 * Killed Bomb Carrier
 * Bomb Planted