Franky's moveset. Every attack ends in a pose, and they work in as much of his quirkiness as possible. Even the infamous Coup de Boo.
Robin's second-tier Super Attack, Dos Fleur: Grab. The bad? It only targets one enemy right in front of Robin, and it's easy to misfire. The good? It's an instant kill on anything short of a boss.
If used on a female enemy, they instead get bound by Robin's arms and get spanked.
Most enemies that are Taken for Granite by Hancock take a funny, lovey-dovey pose. This includes emotionless characters like the Pacifista, and even the most serious of characters, like Mihawk. Let that sink in.
Brook's duel with Mihawk doesn't last very long. He parries some of his moves when Mihawk beheads him, then Brook casually shruggs it off saying he's kept alive not because body, muscle or organs, just his soul.
Pulling off Whitebeard's level 2 special in the first and second games is usually awesome, but then there are the times where the camera doesn't move in accordance with his special and just stays behind him, which results in him making a yanking motion which does... apparently nothing, but then all the Mooks suddenly rocket into the sky for no apparent reason.
Bosses have different phrases they say when you fight them as particular characters. Fighting Buggy as Whitebeard makes him panic and shout "I wanna go home!"