I'm trying to avoid recommending games you already have listed here because a lot of good ones have already been covered.
You should look into the weekly PSN sales if you haven't already. Every week there is a sale, and once a month there is a weekend "flash sale" which can have games as low as $1.
Someone mentioned Far Cry 3, but did you try Far Cry 3: ***** Dragon? It's a standalone expansion which keeps the same controls, but you couldn't tell it's a related game. I think I posted the trailer in the games board, but it's hilarious. If you grew up in the 80s/90s you HAVE to check it out. Speaking of 80s, if you watched Transformers, you want to check out Transformers: Devastation. It really looks like you're playing the 80s movie, and they even brought back all voice actors and the music composers!
If you like the adventure games with a puzzle twist like Assassin's creed or Tomb Raider, an oldie that holds up well is Mirror's Edge. I just love the atmosphere in the game and really can't say enough good stuff about it.