Each weapon (including grenades and the whip) has 2 upgrades that count as additional weapons. The upgrades carry over even if you start a new game on another difficulty (on the same save spot).
| Unlockable: | How to unlock: |
| 2nd level Assault Rifle | Box in Mission 5 |
| 2nd level Grenades | Clear Missions 1, 2 and 3 in Normal difficulty (S rank) |
| 2nd level Rocket Launcher | Clear Missions 9, 10 and 11 in Normal difficulty (S rank) |
| 2nd level Shotgun | Box in Mission 11 |
| 2nd level SMG | Box in Mission 3 |
| 2nd level Whip | Clear Missions 5, 6 and 7 in Normal difficulty (S rank) |
| 3rd level Assault Rifle | Beat the game in Ultra difficulty |
| 3rd level Grenades | Clear Missions from 1 to 8 in Hard difficulty (S rank) |
| 3rd level Rocket Launcher | Clear Missions from 1 to 12 in Ultra difficulty (S rank) |
| 3rd level Shotgun | Beat the game in Expert difficulty |
| 3rd level SMG | Beat the game in Hard difficulty |
| 3rd level Whip | Clear Missions from 1 to 8 in Expert difficulty (S rank) |
