Dragon's Dogma random encounter with enemies. Nothing like underestimate them just to eat the dust.

Half-Life 2; when you understand that you're playing on a truly dynamic battlefield with actual physics and an incredible amount of interactivity.

Gears of War 2 horde mode. Still the best I've ever experienced. If not that, the past of Gears 3 where you're defending that base from invasion. I've never been in combat but I can't imagine it being more intense!

God of War: Ascension -Trial of Archimedes on Titan difficulty.

Pandora's Box room BARELY beats out the clone stage in the Ares battle.  I ran out of everything during that part

F.E.A.R.

Just F.E.A.R. in general, because every firefight is a masterpiece.

Blade mode in MGRR.

Uncharted 2. The whole train segment, starting from when the train starts to leave.