To enable this cheat which will help you progress in the game as you don't have to worry about running out of ammo select the grenade symbol at the 'Multiplayer Weapons' menu and then press X on ALL of the weapons that are shown until a symbol appears next to them.

If you want a change of scenery in your game then enter the following codes at the 'Land Generation' option to access the corresponding bonus landscapes.

Unlock 2 Blimps Landscape:
Enter the code igotworms

Unlock 2 Small Islands Landscape:
Enter the code worms3d

Unlock 3 Submarines Landscape:
Enter the code CANDY

Unlock Bridge Level Landscape:
Enter the code paradisecity

Unlock Cube Shaped Island Landscape:
Enter the code Horror

Unlock Frozen Islands Landscape:
Enter the code marijuana

Unlock Tiny Island Landscape:
Enter the code smashsumfruit

Unlock Zombie Islands Landscape:
Enter the code peopleindastreet

Complete the following tasks with the indicated rank to unlock the corresponding weapon scheme.

Unlock Pro Weapon Scheme:
Complete Test Tube Training.

Unlock Sinking Big Weapon Scheme:
Complete To Boldly Go with a Gold rank.

Unlock Sniper Weapon Scheme:
Complete Hook, Line and Skimmer with a Gold rank.

Unlock Sticky Wars Weapon Scheme:
Complete Beef Cake Breakfast Brawl with a Gold rank.

Unlock ALL Action Weapon Scheme:
Complete Hold Until Relieved with a Gold rank.

Complete the following campaigns or challenges to unlock new challenges in the game.

Unlock Super Sheep Challenge 1:
Complete the High Stakes campaign.

Unlock Super Sheep Challenge 2:
Complete the Plaice Holder campaign.

Unlock Super Sheep Challenge 3:
Complete the A Good Nights Sheep campaign.

Unlock Jet Pack Challenge 1:
Complete the Rum Deal campaign.

Unlock Jet Pack Challenge 2:
Complete the In Space, No-One Can Hear You Clean campaign.

Unlock Jet Pack Challenge 3:
Complete the Hold Until Relieved campaign.

Unlock Parachute Challenge 1:
Complete the Falling For You campaign.

Unlock Parachute Challenge 2:
Complete the Worm and the Beanstalk campaign.

Unlock Parachute Challenge 3:
Complete the Costa Del Danger campaign.

Unlock Deathmatch Challenge 1:
Complete the D-Day campaign.

Unlock Deathmatch Challenge 2:
Complete Deathmatch challenge 1.

Unlock Deathmatch Challenge 3:
Complete Deathmatch challenge 2.

Unlock Deathmatch Challenge 4:
Complete Deathmatch challenge 3.

Unlock Deathmatch Challenge 5:
Complete Deathmatch challenge 4.

Unlock Deathmatch Challenge 6:
Complete Deathmatch challenge 5.

Unlock Deathmatch Challenge 7:
Complete Deathmatch challenge 6.

Unlock Deathmatch Challenge 8:
Complete Deathmatch challenge 7.

Unlock Deathmatch Challenge 9:
Complete Deathmatch challenge 8.

Unlock Deathmatch Challenge 10:
Complete Deathmatch challenge 9.

Unlock Super Sheep:
Complete Sheep Challenge 3.

Unlock Banana Bomb:
Complete Shotgun Challenge 3.

Unlock Mad Cows:
Complete Shotgun Challenge 3 with ALL Golds.

Unlock Nuclear Bomb:
Complete Deathmatch Challenge 10 with 10 Golds.