Multiple Kills
Double Kill!
Kill 2 opponents within 4 seconds of each other.
Triple Kill!
Kill 3 opponents within 4 seconds of each other.
Overkill!
Kill 4 opponents within 4 seconds of each other.
Killtacular!
Kill 5 opponents within 4 seconds of each other.
Killtrocity!
Kill 6 opponents within 4 seconds of each other.
Killimanjaro!
Kill 7 opponents within 4 seconds of each other.
Killtastrophe!
Kill 8 opponents within 4 seconds of each other.
Killpocalypse!
Kill 9 opponents within 4 seconds of each other.
Killionaire!
Kill 10 opponents within 4 seconds of each other.
Sprees
Killing Spree!
Kill 5 opponents in a row without dying.
Killing Frenzy!
Kill 10 opponents in a row without dying.
Running Riot!
Kill 15 opponents in a row without dying.
Rampage!
Kill 20 opponents in a row without dying.
Untouchable!
Kill 25 opponents in a row without dying.
Invincible!
Kill 30 people in a row without dying.
Splatter Spree!
Splatter 5 opponents in a row without dying.
Shotgun Spree!
Kill 5 opponents in a row with the shotgun without dying.
Open Season!
Kill 10 opponents in a row with the shotgun without dying.
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.
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.
Unstoppable!
Kill 10 opponents in a row as the Juggernaut without dying.
Perfection!
Win a slayer game with 15 kills or more without dying.
Weapon Specific Kills
Sniper Kill!
Kill an opponent with the Sniper Rifle or Beam Rifle.
Sniper Spree!
Kill 5 opponents in a row with the sniper without dying.
Sharpshooter! - Kill 10 opponents in a row with the sniper without dying.
Beat Down!
Hit and kill an opponent with a melee attack.
Incineration!
Kill an opponent with a flame-based weapon.
Laser Kill!
Get an opponent with the Spartan Laser.
Grenade Stick!
Kill an opponent by sticking them with a sticky or brute grenade.
Assassin!
Hit and kill an opponent with a melee attack from behind.
Objectives
Flag Score!
Score the flag in CTF.
Killed Flag Carrier!
Kill the opponent flag carrier in CTF.
Killed Juggernaut!
Kill the Juggernaut in a Juggernaut game.
Killed VIP!
Kill an opponent's VIP in a VIP game.
Killed Bomb Carrier!
Kill an opponent bomb carrier in Assault.
Bomb Planted!
Plant the bomb in Assault.
Oddball Kill!
Get a melee kill when holding the oddball.
Flag Kill!
Get a melee kill with the flag.
Hail to the King!
Kill 5 opponents in a row from inside the hill without dying before it moves.
Vehicle Kills
Highjacker!
Board an enemy ground vehicle.
Skyjacker!
Board an aircraft by forcably removing your opponent from it.
Wheelman!
Be the driver of a vehicle when a passenger kills an opponent.
Splatter!
Hit and kill an opponent with a vehicle.
Vehicular Manslaughter!
Splatter 10 opponents in a row with a vehicle without dying.
Misc
Linktacular!
Play in a matchmade game comprised of all Bungie.net users.
Death from the Grave!
Kill an opponent after you have died.
Killjoy!
End an opponent's killing spree, any spree.
Steaktacular!
Luke owes you a steak dinner. (Win a game of matchmaking by more than 25 points)
Bulltrue!
Killed an opponent that was in the act of a sword lunge.
Extermination!
Get an overkill on the opposing team, resulting in the entire team being dead at the same time.
Last Man Standing!
Be the last human alive in an infection game.
Campaign Medals!
Superdetonation!
Score a kill by filling an opponent with enough needles to cause a detonation.
Plasma Combo!
Break an enemies shield and then score a Headshot.
Multikill!
Kill 3+ enemies in 1.5sec to earn a multiplier for all of them.
Headshot!
Kill an enemy with a Headshot.