Syphon Filter : Logan's Shadow
One of best PSP games ever. Already bought mine.

Syphon Filter: Logan's Shadow
This game is great! If you like stealth action games, this game incorporates a lot of the moves familiar in the genre (using cover, silent kills, sniping, etc.), and adds a few new elements beyond the previous syphon filter psp game. the most notable addition is underwater combat, which translates very well onto the psp's button scheme. also, context sensitive button combos add a bit more to the gameplay beyond just pushing the "interact" button and having everything done for you. i like the new music on this games soundtrack over the previous game's. also, the story is very intriguing and involves series supporting characters in a more personal way (you'll see). all worth adding to your psp's game library!