When Darkman first imitates Durant, he takes the necessary steps to fool people into believing the disguise, from recording the voice for practice to making the mask. His first stint as Durant begins with him framing Durant for Armed Robbery. What makes it all the more funny is that the cops immediately arrest the real Durant the next morning while the fake takes his place.
When they run into each other it makes it all the more funny when Guzman tries to figure out which one is Durant.
"You gotta be shitting me!"
During the helicopter scene, Darkman (swinging on the end of a cable) crashes through the window of an office building. He offers a quick apology of "Oh, excuse me!" to the surprised onlookers before he's pulled out of the window again.
After Durant's apparent death, Darkman shouts out, "Burn in hell! Mwahahahaha!" What really sells that line is Liam's Evil Laugh.
The One-Scene Wonder thug, Eddie Black in the opening just every scene with him before you know he gets killed is a laugh riot. Extra props to his phone call.