Unlockables

Armor Permutations Unlockables

Body Pieces: Spartan marked with (S) and Elite marked with (E).

Unlockable	How to Unlock
(E) Ascetic Body	Unlock "Up Close and Personal" Achievement
(E) Ascetic Head	Unlock "Steppin' Razor" Achievement
(E) Ascetic Shoulders	Unlock "Overkill" Achievement
(E) Commando Body	Unlock "Triple Kill" Achievement
(E) Commando Head	Unlock "Overkill" Achievement
(E) Commando Shoulders	Unlock "Killing Frenzy" Achievement
(E) Flight Body	Complete Tsavo Highway On Herioic or Legendary
(E) Flight Head	Complete Campaign mode on Heroic difficulty.
(E) Flight Shoulders	Complete The Ark on Heroic difficulty or higher.
(S) EOD Body	Complete Tsavo Highway on Legendary
(S) EOD Head	Complete Campaign mode on Legendary Difficulty
(S) EOD Shoulders	Complete The Ark on Legendary difficulty
(S) EVA Body	Complete Tsavo Highway on Normal or higher
(S) EVA Head	Complete Campaign mode on Normal
(S) EVA Shoulders	Complete The Ark on Normal difficulty or higher.
(S) Hayabusa Chest	Collect 5 hidden skulls
(S) Hayabusa Helmet	Collect 13 hidden skulls
(S) Hayabusa Shoulders	Collect 9 hidden skulls
(S) Katana	Complete all Achievements (1000/1000)
(S) Mark V Head	Unlock "UNSC Spartan" Achievement
(S) ODST Head	Unlock "Spartan Graduate" Achievement
(S) Rogue Head	Unlock "Spartan Officer" Achievement
(S) Scout Body	Unlock "Too Close to the Sun" Achievement
(S) Scout Head	Unlock "Used Car Salesman" Achievement
(S) Scout Shoulders	Unlock "Mongoose Mowdown" Achievement
(S) Security Head	Earn 1000 Gamerscore points.
(S) Security Shoulders	Currently glitched, no 100% working method to obtain or keep

Multiplayer Medals

If you do the following things you will get the medal while playing multiplayer. When you do the task usually it will show you by a little icon of the said medal appearing in the corner of the screen. Also at the end of each match you can check what medals you got. You can also check your overall medal count on bungie's official website. A very small amount of these are secret medals in that they don't tell you right when you get them but they will appear in your medal history. (One example of such a medal is the Steaktacular! Medal)

Unlockable	How to Unlock
Assassin!	Hit and kill an opponent with a melee attack from behind.
Beat Down!	Hit and kill an opponent with a melee attack.
Bomb Planted!	Plant the bomb in a Assault Gametype.
Bulltrue!	Kill an opponent who is in the act of a sword lunge.
Death from the Grave!	Kill an opponent after you have died.
Double Kill!	Kill 2 opponents within 4 seconds of each other.
Extermination!	Get an overkill on the opposing team, wiping out all of the members.
Flag Kill!	Get a melee kill with the flag in a CTF gametype.
Flag Score!	Capture the opposing team's flag in a CTF gametype.
Grenade Stick!	Kill an opponent by sticking him/her with a Plasma Grenade or a Spike Grenade.
Hail to the King!	Kill 5 consecutive opponents in a single life from inside the hill before it moves in a King of the Hill gametype.
Hell's Janitor!	Kill 10 zombies in a row as a human without dying in an Infection gametype.
Highjacker!	Board an enemy ground vehicle.
Incineration!	Kill an opponent by using the Flamethrower.
Infection Spree!	Kill 5 humans in a row as a zombie without dying in an Infection gametype.
Invincible!	Kill 30 opponents in a row without dying.
Juggernaut Spree!	Kill 5 consecutive opponents in a single run as the Juggernaut in a Juggernaut gametype.
Killapocalypse!	Kill 9 opponents within 4 seconds of each other.
Killed Bomb Carrier!	Kill the opposing bomb carrier in a Assault Gamtype.
Killed Flag Carrier!	Kill the opposing flag carrier in a CTF gametype.
Killed Juggernaut!	Kill the Juggernaut in a Juggernaut gametype.
Killed VIP!	Kill the opposing VIP in a VIP Gametype.
Killimanjaro!	Kill 7 opponents within 4 seconds of each other.
Killing Frenzy!	Kill 10 opponents in a row without dying.
Killing Spree!	Kill 5 opponents in a row without dying.
Killionaire!	Kill 10 opponents within 4 seconds of each other.
Killjoy!	End an opponent's killing spree—any spree.
Killtacular!	Kill 5 opponents within 4 seconds of each other.
Killtastrophe!	Kill 8 opponents within 4 seconds of each other.
Killtrocity!	Kill 6 opponents within 4 seconds of each other.
Laser Kill!	Kill an opponent by using the Spartan Laser.
Last Man Standing!	Be the last human of the game in an Infection gametype.
Linktacular!	Play in a matchmade game comprised of all Bungie.net users. (Secret Medal)
Mmmm Brains!	Kill 10 humans in a row as a zombie without dying in an Infection gametype.
Oddball Kill!	Get a melee kill when holding the ball in a Oddball gametype.
Open Season!	Gun down 10 opponents with a Shotgun in a row without dying.
Overkill!	Kill 4 opponents within 4 seconds of each other.
Perfection!	Win a slayer game with 15+ kills without dying.
Rampage!	Kill 20 opponents in a row without dying.
Running Riot	Kill 15 opponents in a row without dying.
Sharpshooter!	Snipe 10 opponents in a row without dying.
Shotgun Spree!	Gun down 5 opponents with a Shotgun in a row without dying.
Skyjacker!	Board an enemy aircraft.
Slice 'N Dice!	Cut down 10 opponents with the Plasma Sword in a row without dying.
Sniper Kill!	Kill an opponent by using a sniping weapon.
Sniper Spree!	Snipe 5 opponents in a row without dying.
Splatter Spree!	Splatter 5 opponents in a row without dying.
Splatter!	Hit and kill an opponent with a vehicle.
Steaktacular!	Beat the opposing team by over 20 kills; (Luke owes you a steak dinner) (Secret Medal)
Sword Spree!	Cut down 5 opponents with the Plasma Sword in a row without dying.
Triple Kill!	Kill 3 opponents within 4 seconds of each other.
Unstoppable!	Kill 10 consecutive opponents in a single run as the Juggernaut in a Juggernaut gametype.
Untouchable!	Kill 25 opponents in a row without dying.
Vehicular Manslaughter!	Splatter 10 opponents in a row without dying.
Wheelman!	Be the driver of a vehicle when a passenger kills an opponent.
Zombie Killing Spree!	Kill 5 zombies in a row as a human without dying in an Infection gametype.

Multiplayer Ranks

A list of the Skill and Experience needed to advance in rank. Note: you can skip ranks once there is a set skill requirement. For example, many people go from Lieutenant Grade 2 (Skill:10 EXP:85) straight to Captain (Skill:20 EXP:100)

Unlockable	How to Unlock
01 Recruit	Skill Needed: 0 EXP:1
02 Apprentice	Skill Needed: 0 EXP:2
03 Apprentice Grade 2	Skill Needed: 0 EXP:3
04 Private	Skill Needed: 0 EXP:5
05 Private Grade 2	Skill Needed: 0 EXP:7
06 Corporal	Skill Needed: 0 EXP:10
07 Corporal Grade 2	Skill Needed: 0 EXP:15
08 Sergeant	Skill Needed: 0 EXP:20
09 Sergeant Grade 2	Skill Needed: 0 EXP:30
10 Sergeant Grade 3	Skill Needed: 0 EXP:40
11 Gunnery Sergeant	Skill Needed: 0 EXP:50
12 Gunnery Sergeant Grade 2	Skill Needed: 0 EXP:60
13 Gunnery Sergeant Grade 3	Skill Needed: 0 EXP:150
14 Gunnery Sergeant Grade 4	Skill Needed: 0 EXP:300
15 Lieutenant	Skill Needed: 10 EXP:70
16 Lieutenant Grade 2	Skill Needed: 10 EXP:85
17 Lieutenant Grade 3	Skill Needed: 10 EXP:200
18 Lieutenant Grade 4	Skill Needed: 10 EXP:400
19 Captain	Skill Needed: 20 EXP:100
20 Captain Grade 2	Skill Needed: 20 EXP:150
21 Captain Grade 3	Skill Needed: 20 EXP:300
21 Captain Grade 4	Skill Needed: 20 EXP:600
22 Major	Skill Needed: 30 EXP:200
23 Major Grade 2	Skill Needed: 30 EXP:300
24 Major Grade 3	Skill Needed: 30 EXP:600
25 Major Grade 4	Skill Needed: 30 EXP:1,200
26 Commander	Skill Needed: 35 EXP:300
27 Commander Grade 2	Skill Needed: 35 EXP:450
28 Commander Grade 3	Skill Needed: 35 EXP:900
29 Commander Grade 4	Skill Needed: 35 EXP:1,800
30 Colonel	Skill Needed: 40 EXP:400
31 Colonel Grade 2	Skill Needed: 40 EXP:600
32 Colonel Grade 3	Skill Needed: 40 EXP:1,200
33 Colonel Grade 4	Skill Needed: 40 EXP:1,800
34 Brigadier	Skill Needed: 45 EXP:500
35 Brigadier Grade 2	Skill Needed: 45 EXP:1,000
36 Brigadier Grade 3	Skill Needed: 45 EXP:2,000
37 Brigadier Grade 4	Skill Needed: 45 EXP:4,000
38 General	Skill Needed: 50 EXP:600
39 General Grade 2	Skill Needed: 50 EXP:1,200
40 General Grade 3	Skill Needed: 50 EXP:2,500
41 General Grade 4	Skill Needed: 50 EXP:5,000