Suzuka slashing a bus with her katana on the episode that introduced her.
And a dual CMOA for Suzuka and Aisha when they track down and kick the ass of Crackerjack's crew while simultaneously tipping Gene off on his Red Wire Blue Wire dilemma, thus saving the entire city.
Melfina gets one as a Crowning Moment of Funny when she replies to Gene's goading of Crackerjack, utterly deadpan "You know, you really should not aggravate the terrorist."
At the end of the same episode, Gene crashing the Outlaw Star right into the space station, jumping out and KO'ing Crackerjack with one punch.
Basically everything Hilda did was awesome, but her last was probably her best: realizing that she was not going to make it, she immediately grabbed ahold of The Dragon, gave a badass "Facing the Bullets" One-Liner, and then blew the both of them up with a bomb she had hidden in her tooth. "Outlaws never go down easy," indeed.
This troper's personal favorite Hilda moment came in the first part of the first episode. Enemy fighters clamped onto your ship? All your weapons gone? Activate the Sub Ether drive (the Outlaw Star universe variant of Hyperspace; if I've got the term wrong, please correct it) just as the bastards are getting cocky, and obliterate the fighters.
Shimi/Lei Fong effortlessly taking out Jim, Suzuka, and Aisha when they dare to get between him and his duel with Gene.
Pretty much everything Shimi did in his fight with Gene. Made all the more awesome by him being the Badass Normal of the pirates and yet possibly the one who came closest to beating him.
Jim singlehandedly taking out a spacefaring malconent... even though he kind of killed his almost girlfriend accidentally.
The final battle, with Gene and his crew battling a god-like Hazanko in both cyber space and with their ships, the Outlaw Star and Geomancer both getting massive, giant sized upgrades. It ends with the Outlaw Star back to normal size and Gene flying right through Hazanko's head like a bullet.