In any of the three subgames, push ESC to pause, then hold down the R and 2
keys. While holding them, enter the following key combos:
Die Hard 1:
right, up, down, E: god mode.
right, E, down, O: 50 grenades, smoke bombs, etc.
right, up, down, down, E, right: guns (repeat for different guns)
Die Hard 2:
right, up, down, E: guns.
right, E, left, O, A, down, E: tons of missiles and grenades.
Die Hard 3:
left, O, up, down, E, right: infinite lives.