Bonus Airstrike: 
While playing, press Down, Up, Circle, Down, Up, Down, L1. 

Cow Drop:
While playing, press Up, Down, Down, L1, Right. 

Dummy Decoy: 
While playing, press X, L1, Right, Circle, X, Up, Square. 

Hand Grenade: 
While playing, press Triangle, Circle, Square, Square, L1, Right. 

Homing Sniper Grenade: 
While playing, press Left, Up, X, Triangle, L1, L1, Right. 

Level Select: 
At the title screen press Left, Circle, Triangle, Up, and Square 
to make the level select option appear. 

Mortar: 
While playing, press Left, L1, Triangle, Square, Right, Circle, 
Left, Left. 

Most Interesting Bomb:
While playing, press Down, Right, Circle, Circle, Left, Left, 
Up, Square, Triangle. 

Sniper Grenade: 
While playing, press Up, Square, L1, Left, Circle, Triangle, 
Square. 

Super Chain Gun: 
While playing, press Left, L1, Down, Square, Triangle, Up, 
Down. 

Thumper Weapon: 
While playing, press Down, Up, Left, Left, Triangle, Up, 
Right, Down. 

Twister Weapon: 
While playing, press Down, L1, Square, Triangle, Right, 
Up, X.