At  any  in-game  phone  enter  the  number and you will unlock 
a special Darkling.

Cheat code:        Effect:
555-GAME           Unlocks Special 2K Darkling
555-5664           Unlocks the European Retailer (Golfer) 
                   Special Darkling

Phone Numbers
     Use  any  phone in the game and dial these numbers to unlock more
secret achievements.

* 555-1037
* 555-1847
* 555-1206
* 555-1233
* 555-2309
* 555-2349
* 555-2402
* 555-3243
* 555-3285
* 555-3840
* 555-3947
* 555-4372
* 555-4565
* 555-4569
* 555-5289
* 555-5723
* 555-6118
* 555-6205
* 555-6322
* 555-6325
* 555-6557
* 555-6667
* 555-6893
* 555-6969
* 555-7613
* 555-7658
* 555-7892
* 555-7934
* 555-8024
* 555-8930
* 555-9132
* 555-9528
* 555-9562
* 555-9723
* 555-9898
* 555-9985


Achievements
     Complete each achievement to get the allotted gamerscore.

Anti Air (15): 
     Bring down the Chopper

Anti Hero (25): 
     Complete game on normal setting

Bringing People Together (5): 
     Trap 5 enemies within a Black Hole

Bullet Dodger (20): 
     Finish  a multiplayer match with less than 5 deaths (minimum of 4
players)

Butcher (25): 
     Claim 20 Killing Streaks in multiplayer

Cannibal (25): 
     Devour 300 enemies

Completionist (20): 
     Unlock 100 collectables

Contract Killer (25): 
     Be on the winning side in 50 multiplayer matches

Darkness Master (100): 
     Only for those who are completely in tune with the Darkness

Executioner (10): 
     Kill 25 enemies using execution moves

Fashionable (25): 
     Collect all the Darkling outfits

Flag Owner (10): 
     Capture 50 flags in a CTF match

Flag Runner (5): 
     Capture 20 flags in a CTF match

Gatherer (5): 
     Unlock 25 collectables

Ghandi (10): 
     Find a peaceful solution. At least momentarily

Gunner (15): 
     Kill 30 enemies using Darkness Guns

Gunslinger (25): 
     Kill 7 enemies within 15 seconds

Hard to Kill (5): 
     Take enough damage without dying within a multiplayer match

Heart of Gold (50): 
     Help those in need

Henchman (15): 
     Be on the winning side in 20 multiplayer matches

Hoodlum (5): 
     Be  on  the  winning  side  in  a multiplayer match in any of the
multiplayer modes

Knuckle, Meet Face (5): 
     Perform a melee kill for the first time

Legendary Dark (35): 
     Complete game on hard setting

Legendary Executioner (20): 
     Kill 50 enemies using execution moves

Legendary Summoner (25): 
     Summon 50 Darklings

Made Man (35): 
     Be on the winning side in 100 multiplayer matches

Mook (5): 
     Be on the winning side in 5 multiplayer matches

Murderer (5): 
     Claim 20 Killing Streaks in multiplayer

Patriot (5): 
     Capture a flag in a CTF match

Picking Up Stuff (5): 
     Unlock a collectable for the first time

Ripper (15): 
     Kill 30 enemies using Demon Arm

Roadkill (10): 
     Kill the workers in the tunnel

Rogue Killer (15): 
     Kill 15 enemies using Creeping Dark

Romantic (10): 
     Real guys stick around for their ladies

Summoner (5): 
     Summon 5 Darklings

Take a Look at the Sky (50): 
     Take down 6 airplanes

The Collector (10): 
     Unlock 50 collectables

The Don (45): 
     Be on the winning side in 250 multiplayer matches

The Obsessive Collector (15): 
     Unlock 75 collectables

Up Close and Personal (5): 
     Perform an execution move for the first time

Void Bringer (15): 
     Kill 20 enemies using Black Hole


Unlock Collectables 
     Simply  enter  the  phone  number at any payphone from within the
game  to unlock a collectable and remember there are acheivment points
for  collecting  1,  25,  50,  and  100  collectables.  Thats  4  EASY
acheivments totalling 40 points, not to mention the hours of searching
to find the numbers in game!

Unlockable         How to Unlock 
Collectable 10     5556118 
Collectable 08     5554682 
Collectable 07     5554676 
Collectable 06     5554649 
Collectable 05     5554603 
Collectable 04     5554569 
Collectable 09     5554691 
Collectable 03     5554565 
Collectable 02     5554525 
Collectable 01     5554463