Juba, upon seeing the coliseum: "I didn't know men could build such things."
Maximus: "My name is Gladiator." [turns away]
Commodus: "How dare you show your back to me! Slave, you will remove your helmet and tell me your name."
Maximus:[removes helmet and faces Commodus] "My name is Maximus Decimus Meridius, commander of the Armies of the North, General of the Felix Legions, loyal servant to the true emperor, Marcus Aurelius. Father to a murdered son, husband to a murdered wife. And I will have my vengeance, in this life or the next."
"At my signal, unleash hell."
The second Zucchabar arena fight, where Maximus stabs a guy in the chest with two sword, then pulls both of them out and decapitates him.
The same fight has him kill six men in less than a minute. In a "blink or you'll miss it" moment, he takes down a helmeted gladiator by punching him in the head with his less dominant hand. Maximus is just that manly.
Maximus dispatching all the praetorians sent to kill him.
The captain of Commodus' personal guard gets his when he finally stands up to the humiliation and corruption of his ruler. Commodus has been disarmed, and he demands a sword, so the guards begin drawing their blades, only for the captain to step forward and yell "Sheathe your swords!" Then he turns to look at Commodus, and his expression says it all: Time for you to fight your own battles, you bastard." Commodus is promptly so desperate that he finally drops all pretense of fair play and brandishes a dagger. And still gets his ass handed to him.
What possibly makes this even more awesome is that it's actually historically accurate. The Praetorian Guard really did have a history of betraying their Emperor if/when they finally go too far, and Commudus certainly did. However, while it's historically accurate in the sense that the Praetorians were known to turn against the higher-ups if given sufficient reason to do so, it's not how the real Commodus died; he was strangled by an assassin.