This entry needs to be rewritten to remove the scanlation links and provide the necessary context.
Oh, Crap!: Rob Lucci who remained calm and determined during the extremely long and grueling fight with Luffy, finally was shocked to the core in the last seconds of the fight when Luffy refused to fall down even after taking his ultimate attack (much weaker version of which disabled Luffy for a time just a few minutes earlier) straight to the chest.
This is Eneru's reaction on realizing his lightning-based Devil Fruit powers have no effect on Luffy, whose own fruit power has made his body into rubber (with rubber being a good insulator for electricity).
In episode 484, Akainu gives off two of these—one right as Whitebeard appears behind him, and one right before he's sent smashing into the ground by Whitebeard.
Ms. Goldenweek gives a pretty good one when she realizes that Usopp's about to burn off her hypnotic symbol that was keeping Luffy from ruining the entire Little Garden operation. Oh crap indeed.
Arlong has a minor one when he removes Zoro's bandages in episode 41 and wonders how he's still standing.
The usually-stoic Zoro gives one when he realizes that Pica's plan when fighting him was to lure him far away from Usopp, Riku and the others so he couldn't save them in time. Zoro gets over it quickly enough, though.
This entry needs to be rewritten to remove the scanlation links and provide the necessary context.