Awesome / Grand Theft Auto IV: The Ballad of Gay Tony
The ending of Momma's Boy if Luis does not take a dive. The loan shark confronts him after the fight and Luis responds by blowing him away.
When Brucie, whose entire lifestyle is revealed to be compensation for feeling inferior to his older, generally atrocious brother Mori, finally punches Mori in the face and Mori cries like a baby. You can't help but cheer for Brucie baby!
The mission "Boulevard Baby". We see Roman, pretty much the entire series' butt monkey, stroll up to the bouncer of Maisonette 9. He shows him his ID and is accepted into the club.
It speaks volumes about a character when their Crowning Moment of Awesome is NOT failing to walk through a door.
The mission "High Dive", the first time you climb up to the very top of the Empire State Building Rotterdam Tower, via the new ladder on the spire.
Take note, this is also the mission in which the Explosive Shotgun is introduced. So the entire time you're climbing up to the top of the spire, you're blasting dozens of NOOSE agents to smithereens and shooting their helicopters out of the sky.
"Sexy Time". Sneak onto a yacht chartered by some shady Arms Dealers. Steal the prototype attack helicopter they have parked on board. Use the helicopter's missiles to sink the yacht. Cut the gun runners escaping on lifeboats down with the choppers' miniguns. Need any more be said?
The final mission. Blow up some drug vans at a fairground, then jump on your motorcycle and drive down the freeway to the airport with Yusuf blowing up enemies with air to surface rockets from a gold-plated attack helicopter. Then jump onto a taking off jet, blow it up with a grenade and then parachute unharmed to a park while rocking out to the awesome song No Security.