PS2 Batman Begins Cheats

[Lawrence]

Don't die in gas filled rooms:
When in a gas (or smoke) filled room, start rolling around (R2 + direction). Apparently while rolling Batman doesn't need to breathe. So you won't lose any health due to the gas. This can be very helpful when low on health.

Bonus unlockables:
When you beat the game, you unlock several things. It doesn't matter which difficulty.

Unlock everything in Gallery of Fear - Beat the game once
Unlock 2 Batmobile missions - Beat the game once
Unlock all movies and interviews - Beat the game once
Unlock 3 alternate Batsuits - Beat the game once
Prototype Batmobile (the one with camouflage paint) - Beat the Batmobile missions

Source