Unlock All Game Maps
To unlock all of the maps in the game, from the main menu simply enter the "Options" menu, then find the "Cheats" section. Enter "GiveMeTheMaps" into the form and you will have all levels. The code is case-sensitive so make sure to enter it exactly as shown. Also, be sure you want to unlock all levels, because there is no way to undo this without starting an entirely new game.
Non-Working Cheats
If you do a quick Internet search for Far Cry Vengeance cheats, you may come up with some promising-sounding results. However, aside from the maps code listed above, none of the cheats that are said to work for this game actually work. This is because, for some reason, codes for an older Far Cry game have been misclassified as Far Cry Vengeance cheats. Some speculate that the cheats were active in a prerelease build of the game, but were taken out before the final release. Whatever the reason, don't bother with these cheats, because they simply don't work.
Easy Adrenaline
Adrenaline is used in the game to signify how close Jack is to being able to unleash his feral abilities. The game becomes much easier when Jack goes feral and it also equals much more fun. There are a few ways to build up your adrenaline fairly quickly. The first one is to get as many head shots as you can. For this, a smaller gun like a pistol is recommended for its accuracy. You can also build adrenaline by attacking enemies with your combat knife or claws.
Strategized Weaponry
Though you can only carry two guns, Far Cry Vengeance offers quite a few methods of attack that can save you precious ammo. For starters, use your feral powers when you're going up against a large number of enemies, as this will save you both health and ammo. With secondary weapons, head shots are best as they deal the most damage these fairly weak weapons can deliver. Later in the game, once you've unlocked the ability, Jack can go into feral mode and rip stationary guns, such as machine gun turrets and grenade-launching turrets. These are advantageous to use whenever possible, as they deal major damage.