Pause the game, then access the cell phone. Select "Dial", then enter one of the following numbers, including the # symbol, and choose "Call". If you entered the code correctly, a message will appear. Then, go to "Cheats", and select the now unlocked option.
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Player Ability

Full Health -- #1

Car Mass (increased mass for harder collisions) -- #2

Milk Bones (increased melee attack damage) -- #3

Add Police Notoriety (+1 star to police wanted meter) -- #4

Player Pratfalls -- #5

Infinite Sprint -- #6

Unlimited Clip (never reload, except for RPGs) -- #9

Infinite Ammo -- #11

Heaven Bound (killed bodies float upward) -- #12

Add Gang Notoriety (+1 gang attack level) -- #35

Never Die -- #36

No Cop Notoriety -- #50

No Gang Notoriety -- #51

I Am Giant (become very tall) -- #200

Itty Bitty (become very short) -- #201

Give Cash (gain $1,000) -- #2274666399

 

Vehicles

Repair Car (fixes car, boat, and helicopter damage) -- #1056

Ambulance -- #1040

Anchor -- #1041

Atlasbreaker -- #1042

Attrazione -- #1043

Backdraft -- #1044

Backhoe -- #1045

Bag Boy -- #1046

Baron -- #1047

Bear -- #1048

Bootlegger -- #1049

Bulldog -- #1050

Bulldozer -- #1051

Compton -- #1052

Eiswolf -- #1053

FBI -- #1054

Five0 -- #1055

Hollywood -- #1057

Justice -- #1058

Kent -- #1059

Mag -- #1060

Mixmaster -- #1061

Mongoose -- #1062

Oring -- #1063

Phoenix -- #1064

Quasar -- #1065

Quota -- #1066

Rampage -- #1067

Raycaster -- #1068

Reaper -- #1069

Septic Avenger -- #1070

Shaft -- #1071

Stilwater Municipal -- #1072

Superiore -- #1073

Taxi -- #1074

The Job -- #1075

Titan -- #1076

Toad -- #1077

Varsity -- #1078

Venom Classic -- #1079

Vortex -- #1080

Zenith -- #1081

Horizon (commerical helicopter) -- #711

Snipes57 (executive private jet) -- #712

Tornado (police helicopter with minigun and anti-tank missiles; can lock onto other vehicles or be manually aimed) -- #713

Wolverine (P-51 Mustang-style airplane with machine gun) -- #714

Kaneda (custom street racing motorcycle) -- #801

Kenshin (street racing motorcycle) -- #802

Melbourne (Harley-style motorcycle) -- #803

Sabretooth (custom...