Larry gets his where he beats a sword-wielding Pharaoh with nothing but a flashlight. For added epic, if you pay attention you'll notice Larry's arm literally shaking from the effort of fending off Kahmunrah's Egyptian-sword. He's up against somebody obviously much stronger than him, and he still kicks Kahmunrah's ass. And, to reiterate, with a flashlight.
Custer: We are NOT going to attack... right... now! (they attack)
Lincoln shows up and proceeds to curb-stomp an army of Underworld demons.
How Larry dealt with Kahmunrah at the beginning of the film was also kind of awesome. He was completely unimpressed by the man due to his previous experience at the museum, deflating some of his thunder and ruining his attempt to intimidate Larry. Then he managed to outwit the pharaoh long enough to set the octopus on him and snag the tablet back.
Secret of the Tomb:
Lancelot's introduction. He punches out the Triceratops. And before that, when it attempts to strike him, he backflips over it. In slow motion.
The entire fight with the bronze statue of the nine-headed Xiangliu. First, Lancelot shows off his badass sword-fighting skills, while Nick demonstrates his skill with a dagger, from playing World of Warcraft. Of course, the statue's made of metal and doesn't get any damage from their blades...but Larry proceeds to shock it into submission with a defibrillator.
Tilly attempts to knock out Attila when Nick and Attila lock her in. She hits him on the forehead with a claw hammer...which does absolutely no damage at all. No bruises, no reaction, nothing.
Doesn't help that she hit his helmet rather than any actual "flesh"
The dance party at the end. Bonus points for the Union Soldier doing the worm at the credits and the Triceratops lifting up Rexy.
Hugh Jackman's surprise appearance. As himself, no less. Playing King Arthur.