GTA4 - 8 on 8 Team Deathmatch:
Epic urban warfare. Escalade with 3 enemies comes at me. I fire the rocket launcher without aiming at the oncoming car, a mere 30 feet away. The missile strikes the hood, the vehicle flips in the air, over my head and lands in a pile of debris behind me. That was incredible!
GTA4 Multiplayer again:
I collide head on with an enemy in a car. He flies through the windshield, bounces off my car and gets run over by his teammates that were chasing me. Hysterical.
GTA4:
The bank robbery mission. Sorry, GTA4 is awesome.
Gears of War:
Co-op on Nightmare difficulty with a buddy. That is some awesome QT.
Fallout 3:
Blowing up Megaton. That was just nuts!
World of Warcraft:
When we first beat C'Thun. Talk about geek-fest in vent.
Diablo 3:
Lord of Destruction: The Baal cinematic.
Left 4 Dead:
No Mercy Campaign, Versus Mode. The enemy gets a Tank in the very beginning. Two get killed, we make it to elevator, the third gets killed halfway through event. I am the sole survivor in the elevator going up. I come out, Smoker grabs me at close range, I melee him. As I am meleeing him, a Hunter pounces and gets caught by the same melee. I kill them both. I spot the boomer's fatass around the corner, I shoot him, avoiding vomit. Then I just run, meleeing, shooting, trying to get to safe room before they respawn. A second tank comes at me at the second right turn, I manage to duck past him, and book it all the way to the safe room and shut the door. Best. Game. Ever.
Left 4 Dead:
No Mercy, Versus. All survivors are at low health, I get tank at the very end. As the chopper is landing, I chuck a piece of concrete at the bunched up survivors, they all collapse, and the infected win! A lot of cursing followed.!