Tomb -
Easy-1min (paintball cheat)
Normal-2min35secs (priestess character)
Hard-2min20secs (teeth mummy character)

Chinese Chef
Complete the 1970 Chinese level in story mode under the easy difficulty setting to unlock Chinese Chef in arcade mode.

Cultist
Complete the 1935 Tomb level in story mode under the easy difficulty setting to unlock Cultist in arcade mode.

Chinese -
Easy-1min (chinese waiter character)
Normal-2min35secs (gun sounds cheat)
Hard-6min5secs (mr. big character)

Extra Arcade Mode features
Complete the 1st 3 levels in story mode to unlock the Village, Chemical Plant, and Planet-X levels in arcade mode. Additionally, Dr. Seth Graven, Dr. Katje Nadir, Fingers McKenzie, Ravelle Velvet, Sebastian Photon, and Angel Perez Bots will also be unlocked as playable characters in arcade mode.

Quick Time Unlocks
You can get extra cheats and characters if you win the following times on levels:
[PS2 Cheat by: Markus]

Badass Cyborg
Complete the 2005 Cyberden level in story mode under the easy difficulty setting to unlock Badass Cyborg in arcade mode.

PS2 Cheats for Time Splitters

Time Splitters cheat codes

Time Splitters cheats