Tenchu: Time of the Assassins for the PSP only £12.99 from Blahdvd - cheapest elsewhere is £20
Description from Amazon:
-Scenario mode brand new storylines with your favourite Tenchu characters
-Make your own missions and levels and exchange them with your friends!
-A variety of high-quality single-player and multiplayer modes.
-Features a level editor that players can use to create new missions, and then share with friends.
-Stealth kills demand a high level of skill, and offer a rewarding challenge.
-50 extra standalone missions and four main characters plus one new character.
-Over 40 NPCs including allies and enemies from previous Tenchu titles.