Awesome, just awesome shooting game.
You progress through the levels by taking down helicopters and other enemies, while using BEAST weapons like your everyday pistol and SMG, and also A-Bomb Launchers and Black Hole Generators.
Here are some "cheats" (Unlocks guns)
Enter them through the Players>Cheats from the main menu.
Bow/Arrow - John Rambo
Chain Gun - Old Faithful
Sniper Rifle - Its a Jackal
Double Shotgun - This is my boomstick
Guided Launcher - Follow the leader
Drunken Launcher - Moonshine
GooGun - Gloop
Spark Plug - 9 Volt
Laser Rifle - Alpha
Auto Laser Rifle - Beta
Laser Shotgun - Gamma
Anytime - I dont have time to bleed
Airstrike - Call in artillery
All Levels - You are the moon master
A-Bomb Launcher - Missile launch detected
Soundwaave - Bass in your face
Canyon Lands - Aint no mountain high enough
Underground Lab - Who rides the wrecking ball
Flak Cannon - Shrapnel
Black Hole Generator - Wash away the rain
Amazon Jungle - Ive got jungle fever
Bladerang - Australians all let us rejoice
*Note*
Unlock does NOT mean you get it as soon as you start. It means you have a chance of getting it as an enemy drop. Otherwise, you have to wait for the level that gives the weapon, before it's dropped at all.