Anytime Dan takes down a boss, but especially the Spider, Tsar Runner and Philips.
The entire fight from finding out Faye is a Hybrid to the room where you meet the Amada AI. Dan - and most likely the player - is royally pissed, and you've most likely fully upgraded your weapons and nanomachines at this point so that you practically define Lightning Bruiser. Then a bunch of robots come in, nicely bunched up. Awesomeness ensues, and it's almost as if Dan is in pure Unstoppable Rage, shock-bursting, meleeing, and gunning his way through dozens upon dozens of robots. It's actually moderately easy to get a good ways ahead of the rest of the team (even on medium difficulty), meaning that unless you get taken down, by the time you get to the next cutscene, Dan pretty much carved his way through the entire enemy force by himself.
The one-on-one fights between Beetle Team and the Shinobi-Faye force. While Dan and Faye are fighting hand-to-hand, Charlie, Bo, and Rachel each take down a Shinobi in close combat. Charlie's involves ramming the thing into a wall and emptying his SMG into its face at point-blank range.