Sanctuary-17 is a free flash game that has pixelated graphics and a lot of tension, you are one of the last remaining survivors after robots went insane and destroyed humanity or something like that. At it's core Sanctuary-17 is a simple top down shooter, you can move, shoot and use a shield for protection which you should really use because this a one hit kill type of game, that's where the tension comes from. The combination of limited vision because of the darkness, the sound and the knowledge of robots lurking around make for a surprisingly unnerving experience of course this can also make the game frustating when you get killed which trust me, it will happen.
 
Play  Sanctuary-17 for free here