Just Cause 2 (during long treks away from quests. Sometimes, I'll catch myself thinking of grappling routes when walking around)
Fallout 3 (rushing into the Anchorage memorial, dodging Mireluks just so I can get that extra bonus, planting an observer, and turning into a Mireluk hunter. Running for my life, popping stimpaks and dog meat, or taking down raiders at 100 yards to fry some slaves.)
InFamous (sliding on powercables, jumping off into a crowd of reapers, switching on polarity wall, then using precision from behind cover, only to turn to see a mob coming after me...)
Republic Commando (No game has filled me with so much panic at seeing a squadmate fall. Or filled me with quite as much satisfaction as having my carefully placed squad target a single enemy, with deadly precision)
S.L.A.I (PS2 game that is still one of my top 5) (Jumping across buildings, running for my life from a Hartman as fast as my Proton can carry me, or working out the best combination of weapons. Or hiding in a corner with camo on, just to hit a boss with a well placed shotgun blast to the back...)