Complete the indicated game to unlock the corresponding weapon.

Chicago Typewriter in Separate Ways: Complete Separate Ways mode.
Handcannon: Earn a "five star" rank for each Mercenaries mode level.
Infinite Rocket Launcher in New Game +: Complete the game.
Matilda in New Game +: Complete the game.
P.R.L. 412 in New Game +: Complete the game under the Professional difficulty.