At the main menu, go to the dropship, then enter one of the following codes to activate the corresponding cheat function:

Black Widow auto-pistol - Enter "13374877" as a code to unlock the Black Widow auto-pistol.
Captain's armor - Enter "17013214" as a code to unlock the Captain's armor. Repeat the code to disable its effect.

Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

With All Due Haste (25 points): Capture the Missile Silo on "Nuclear Dawn" in under 8 minutes on hard difficulty.
Lightning Assault (25 points): Capture the Munitions Facility in Blackstone Marsh within 4 minutes of hacking the Heavy.
Mission Accomplished (30 points): Complete the campaign on any difficulty.
Over Achiever (50 points): Complete the campaign on hard difficulty.
To the Delphi Main (20 points): Complete the first half of the campaign on any difficulty.
First Drop (10 points): Complete the first mission of the campaign on any difficulty.
You're Doing It Right (25 points): Finish in first place on the winning team in a ranked match.
Badge Expert (35 points): Earn each badge in ranked matches.
Feat Expert (20 points): Earn each feat in ranked matches.
Badge Collector (15 points): Earn 5 unique badges in ranked matches.
Feat Collector (10 points): Earn 5 unique feats in ranked matches.
Never Tell Me the Odds (15 points): Win a game with Swarm mode.
3,720 to 1 (50 points): Win a game with Super Swarm mode.
Top Brass (50 points): Reach level 50 in ranked matches.
Rising Star (30 points): Reach level 25 in ranked matches.
Ding! (15 points): Reach level 5 in ranked matches.
Instant Gratification (10 points): Win an instant action game.
Plays Well with Others (10 points): Win a ranked match.
Boom Goes the Dynamite (30 points): Kill 3 players at once with explosions.
Bane of the Immobile (20 points): Destroy 30 turrets.
Veni, Vidi, Vici. (20 points): Win a ranked match on all maps.
Blades 'n 'Nades (30 points): Kill 5 players in a row with only Grenades and Knives in a ranked match.
Blood Lust (15 points): Kill 100 players in ranked matches.
Test Drive (10 points): Get a kill with every vehicle weapon.
Excessive Celebration (10 points): Perform a fatality with the Heavy Armor.
Steamroll (10 points): Kill a player by crushing them with a Tank.
This Is My Rifle (20 points): Kill 30 players with an Assault Rifle.
Ain't Got Time to Bleed (20 points): Kill 30 players with a Machine Gun.
Feeling Lucky? (20 points): Kill 30 players with a Pistol.
Ventilator (20 points): Kill 30 players with a Shotgun.
It's a Legitimate Strategy (20 points): Kill 30 players with a Sniper Rifle.
Repo Man (20 points): Destroy 30 vehicles.
Public Housing Authority (10 points): Place a deployable within 50m of another deployable.
Improvised Orbital Cannon (15 points): Kill an enemy player by dropping a deployable on them.
Sherman's March (15 points): Capture a point when all of its structures are destroyed in Conquest.
Silent but Deadly (15 points): Deploy a sensor array within 50m of enemy CP.
We Have Won (20 points): Overdrive for 280 km.
Goal Oriented (25 points): Participate in all DCMs in the game successfully.
Cutting to the Chase (20 points): Win a ranked match in under 14 minutes.
Adaptable (15 points): Participate in a successful DCM.
Swatting at Flies (10 points): Destroy a non-friendly repair drone.
Recession Proof (10 points): Purchase one of every vehicle and deployable.
Passive Aggressive (10 points): Customize passive modules for one loadout in game.
Shop 'til you drop (10 points): Change loadouts 3 times.
Desensitization (15 points): Destroy 10 Sensor Arrays or Micro Sensors in ranked matches.
Ringleader (30 points): Invite 10 players into your squad (and have them accept) in multiplayer.
Blitzkrieg (50 points): Capture 2 Control Points within 3 minutes in a ranked match.
Mr. Fixit (20 points): Get 100 Repairs.

Additionally, there are two secret achievements:

Secret achievement (0 points): Unknown.
Secret achievement (0 points): Unknown.