More of a PSP oriented series now isn't it? I think there's been a few that's came out on it. I remember playing the demo for the first Syphon Filter way back in the day, because for its time it had a really progressive and modern lock-on system, combined with manual aiming for effective headshots. It was a slick series back in its day. I actually remember arguing with my mates which was better, Syphon Filter or Metal Gear Solid. They both just came out and neither started being really big yet, so there were genuine debate over which was the better action game.
Good stuff good stuff.