When Beck and Cutler are fighting Paige at the docks, they throw their discs to cut the lines of the shipping container they're riding. When the discs come back, they catch each others' discs, leading to an awkward moment where they have to trade back mid-battle.
Zed booting Hopper out of the car in "The Reward".
Paige making Pavel smack his face into a windshield during "Scars, Part 1".
The Disney XD previews for the next episode that air during the credits frequently turn Beck into the Butt Monkey.
"Grounded". Beck's reaction to Tesler bringing a BFG to their fight.
Beck insists to Tron that his meeting up with Paige in "Rendezvous" is not a date, but merely him gathering intel on the enemy. He does this whilst checking his reflection to make sure his hair is presentable. Tron naturally, doesn't buy it for a second. The entire dialogue is just hilarious:
Paige: Bet this is your first time taking a nose dive out of a helicopter. Beck: *Aside Glance* note Beck's first time doing this was actually during the first episode, after his first confrontation with Paige no less
It's Black Comedy to a degree, but when Mara tells Zed the renegade should walk in and say he killed Able himself, Beck chooses that exact moment to walk in and announce his opinion.