IllegalPaladin on 24 March 2009
By collecting treasures, you unlock stuff like alternate costumes, alternate post processing modes (like the humurous 'next-gen' look), playing the game in a 'mirror world', making of cut-scene videos, artwork, slow motion mode, the ability to equip any weapon (assuming you've unlocked it of course) and unlimited ammo.
I'm sure there's some other ones.
