Killing Spree!Killing Spree! Medal

Kill 5 opponents in a row without dying.

 

Killing Frenzy!
Killing Frenzy! Medal

Kill 10 opponents in a row without dying.

 

Running Riot!
Running Riot! Medal

Kill 15 opponents in a row without dying. 

 

Rampage!
Rampage! Medal

Kill 20 opponents in a row without dying.

 

Untouchable!
Untouchable! Medal

Kill 25 opponents in a row without dying.

 

Invincible!
Invincible! Medal

Kill 30 opponents in a row without dying.

 

Killjoy!
Killjoy! Medal

End an opponent's killing spree - any spree.

 

Shotgun Spree!
Shotgun Spree! Medal

Kill 5 opponents in a row with a shotgun without dying.

 

Open Season! (Formerly named Cheneymania!)
Chenymania! Medal

Kill 10 opponents in a row with a shotgun without dying.

 

Sniper Kill!
Sniper Kill! Medal

Kill an opponent with a Sniper Rifle or Beam Rifle.

 

Sniper Spree!
Sniper Spree! Medal

Kill 5 opponents in a row with a sniper weapon without dying.

 

Sharpshooter!
Sharpshooter! Medal

Kill 10 opponents in a row with a sniper weapon without dying.

 

Double Kill!
Double Kill! Medal

Kill 2 opponents within 4 seconds of the previous kill.

 

Triple Kill!
Triple Kill! Medal

Kill 3 opponents within 4 seconds of the previous kill.

 

Overkill!
Overkill! Medal

Kill 4 opponents within 4 seconds of the previous kill.

 

Killtacular!
Killtacular! Medal

Kill 5 opponents within 4 seconds of the previous kill.

 

Killtrocity!

Kill 6 opponents within 4 seconds of the previous kill.

 

Killimanjaro!

Kill 7 opponents within 4 seconds of the previous kill.

 

Killtastrophe!
Killtastrophe! Medal

Kill 8 opponents within 4 seconds of the previous kill.

 

Killpocalypse! Killpocalypse! Medal

Kill 9 opponents within 4 seconds of the previous kill.

 

Killionaire!
Killionaire! Medal

Kill 10 opponents within 4 seconds of the previous kill.

 

Laser Kill!
Laser Kill! Medal

Kill an opponent with the Spartan Laser.

 

Grenade Stick!
Grenade Stick! Medal

Kill an opponent by sticking them with a plasma or brute grenade.

 

Beat Down!
Beat Down! Medal

Hit and kill an opponent with a melee attack.

 

Assassin!
Assassin! Medal

Hit and kill an opponent with a melee attack from behind.

 

Hijacker!
Hijacker! Medal

Board a vehicle.

 

Skyjacker!Skyjacker! Medal

Board an aircraft by forcably removing the opponent in it.

 

Wheelman!
Wheelman! Medal

Be the driver of a vehicle when a passanger kills an opponent.

 

Splatter!
Splatter! Medal

Hit and kill an opponent with a vehicle.

 

Splatter Spree!
Splatter Spree!

Splatter 5 opponents in a row with a vehicle without dying.

 

Vehicular Manslaughter!
Vehicular Manslaughter! 

Medal

Splatter 10 opponents in a row with a vehicle without dying.

 

Death From the Grave
Death from the Grave

Kill an opponent after you have died.

 

Extermination!
Extermination! Medal

Get an overkill on the opposing team that results in all of the team being dead.

 

Perfection!
Perfection! Medal

Win a slayer game with a score of 15 or more kills without dying.

 

Hail to the King!

Kill five opponents in the hill without dying and the hill moving.

 

Killed VIP!
Killed VIP! Medal

Kill an opponent's VIP in a VIP game.

 

Killed Flag Carrier!
Killed Flag Carrier! 

Medal

Kill the opponent flag carrier in CTF.

 

Flag Kill!
Flag Kill! Medal

Get a melee kill with the flag.

 

Flag Score!
Flag Score! Medal

Score the flag in CTF.

 

Killed Bomb Carrier!
Killed Bomb Carrier! 

Medal

Kill an opponent bomb carrier in Assault.

 

Bomb Planted!Bomb Planted! Medal

Plant the bomb in Assualt.

 

Oddball Kill!
Oddball Kill! Medal

Get a melee kill while holding the oddball.

 

Unconfirmed, but detected in code for Halo 3 Beta.

Killed Juggernaut!
Kill the Juggernaut in a Juggernaut game.

Bulltrue!
Killed an opponent that was in the act of a sword lunge.

Incineration!
Kill an opponent with a flame-based weapon.

Last Man Standing!
Be the last human in an infection game.

Sword Spree!
Kill 5 opponents in a row with the sword without dying.

Slice 'n Dice!
Kill 10 opponents in a row with the sword without dying.

Juggernaut Spree!
Kill 5 opponents in a row as the Juggernaut without dying.

Unstoppable!
Kill 10 opponents in a row as the Juggernaut without dying.

Infection Spree!
Kill 5 humans in a row as the zombie without dying.

Mmmm Brains!
Kill 10 humans in a row as the zombie without dying.

Zombie Killing Spree!
Kill 5 zombies in a row as the human without dying.

Hell's Janitor!
Kill 10 zombies in a row as the human without dying.

Is Quisnam Protero Damno!
Kill 15 zombies in a row as the human without dying. 

 

Medal images and medal descriptions provided by Bungie.