Have to echo the DMC3 sentiment. Especially the fight with Arkham. I just replay Mission 19 over and over again. Also, the second clash with Vergil is a roughly equal dose of badassery.
I mean, in the cutscenes before the fight with Arkham, Dante and Arkham both laugh like the both got high off of psilocybin mushrooms, (with Arkham inhaling sulfur hexaflouride beforehand) then Arkham transforms and Dante quips about how his father wasn't as hideous as Arkham's transformation portrays and asks while looking at his own reflection in his sword's blade "Can't you tell by looking at me?" In the cutscene halfway through the battle, Vergil appears, talks some smack and then tells Dante that Arkham shouldn't be the "main event" and Dante responds by telling Vergil he's right. After the brothers open a can of stylish whoop-ass on Arkham, Vergil joins Dante's gun-style finisher and even breaks a brief smile on his face before sending Arkham hurling back to the human world.
During the second Vergil fight, the music, alone, is badass enough to warrant the entire fight epic. After the fight ends, Lady interrupts and fires her Kalina Ann weapon, only to have her missile get sliced into four equal pieces. The last piece of badassery in that scene is where Arkham shows his break dancing skills and catches everyone in his little double spin kick maneuver that sends everyone off of the ascending pillar.
Oh, and playing Borderlands with my Berserker having the "Bad Ass" class mod equipped.