The Final Boss fight against Sullivan, especially if you've been working on your hand to hand combat moves and have acquired the haymaker and double leg drop kick. A hand to hand battle against the Big Bad on top of a building surrounded by a sea of zombies while an AC-130 blows holes in the building in the background... epic. Then there's Sullivan's death. How many other villains get ripped in half by a plane!?
Anytime you use the Blitzkrieg. It's an electric wheelchair with machine guns attached that taunts zombies in the voice of Stephen Hawking!
Player created moment: Delivering the final blow to blow up Tyrone King's helicopter with a book.
Tear Jerker moment aside: Frank West taking on Chuck Greene in Off The Record. Both of Dead Rising's protagonists taking each other on to determine who kicks more ass.
Making it better would be to have a co-op player join you for a good ol' Mirror Match.
Somewhat dampened by the fact that Chuck's already gone insane before the events of Dead Rising 2, meaning he hasn't taken any levels in badass. Due to this, his boss fight is more or less the exact same as Leon's.
Before the fight, Chuck tells Frank that zombies are just a nuisance and people are the real danger. He proves it by casually Neck Lifting a zombie, holding it in place while he continues to talk, and then snapping its neck when he's done.
The final boss fight of Off The Record. To put it into perspective, Stacey knew that she had to deal with Frank West. You know, Frank West, a guy who's covered wars and killed more than 100,000 zombies, insane military officials, Ax-Crazy clowns, corrupt cops among others. So she decided to bring in a freakin' giant robot to kill him. He manages to own it.
A good survivor example would be the band Angel Lust who are found playing a concert, having apparently not even noticed that everyone has become a zombie. After Chuck climbs up on stage to get them to follow him they finish the show by rocking so hard that the crowd of zombies who have gathered below all die from a headsplosion! Then they give you a combo card that allows Chuck to do this!
They also frequently show up right before you fight off TK's mercenary goons robbing the casinos in Fortune City. Give 'em all the dead merc's rifles you have been picking up along the way, and they become your very own elite squad of mercenary-killing British rockers.
When Chuck faces down the man behind the outbreak in Fortune City, the traitorous city guard Sullivan. After a brutal fist fight in which the odds are stacked against Chuck, he knocks Sullivan down but before he can finish him is blasted off his feet by a missile from Sullivan's extraction plane. The agent sends up a skyhook and taunts Chuck, but when he glances at the plane Chuck handcuffs his belt to an iron bar on the roof...just before the plane catches the skyhook. Chuck was right: Sullivan wouldn't make it out in one piece.
The DLC "Case West" has a moment that is the absolute embodiment of this trope. Frank West and Chuck Greene are in the main Phenotrans production facility trying to uncover evidence of the pharmaceutical company's involvement in the outbreak. A lockdown is preventing them from getting to a certain so they have to destroy a generator. After getting the components they need and rigging a bomb on the generator (with a ridiculously short timer, for some reason), they sprint out of the room and are sent sprawling by the explosion. Frank and Chuck slowly pick themselves up off the floor, turn to look back at the burning room, and simultaneously go for a high-five.
You can give the survivors in your party rifles and watch them give the evil redneck snipers a taste of their own medicine.