Especially Jade's—one of the most powerful on your first playthrough, and complete with an awesome incantation: "Oh admonishing melody, arise in the name of the Necromancer! Mystic Cage! Now know what true power is!". Still, Luke's comes at the end when the party is fighting Van for the fifth time or so, Tear is singing the Grand Fonic Hymn, and Luke runs up, slashes Van a bunch, and then unleashes his Mystic Arte, Radiant Howl, finishing with the words "NOW YOU DIE!"
Luke: You're finished! Arise, resound, and become a blade of destruction!LOST FON DRIVE!!
Tear: O light that rains down on heaven and earth bring my enemies to their destined annihilation! FORTUNE'S ARC! And grant us the divine protectine of thine brillance!
Guy: Prepare yourself for a blinding storm! BRILLIANT OVERLORD! Never fight a battle you can't win.
Jade: I, who stand in the full light of the heavens, command thee who opens the gates of Hell. Come forth, divine lightning! This ends now! INDIGNATION!
Anise: Now the fun starts! FEVER TIME BABY, YEAH! And you don't stop!
Asch letting Luke go ahead and making one hell of a Badass Boast.
Asch: No, your fight is with me, Asch! No, Luke fon Fabre! Prepare to die!
He may have died in the process, but he took out every single one of the soldiers, including the ones that caused his death.
Jade's One Shot Kill of the Liger Queen in the anime by using Indignation. Jade also gets the honour of being the only one to damage Van before Luke finishes him in the final battle.
Not to mention his breaking the fon slot seal and one shotting Dist with Mystic Cage. Really, Jade gets the most Moments of Awesome in the anime.
Luke's resolve to take a human life if he has to and dueling the Oracle Knight in the anime. It was badass.
Has anyone noticed how in the Tower of Rem scene where Luke uses the Ten Thousand Replicas, Guy holds down Tear. He touched a girl for the sake of Luke at the moment killing himself. And then remember Guy is still a bit timid around girls...talk about guts.
For a story based example, Jade removes the Fon Slot Seal by himself. Guy mentions that NO SINGLE PERSON IN HISTORY has ever done such a feat. Jade naturally jokes it off as nothing at all.
One long, drawn-out word: REPLICAAAAAAAAAAA!! Not even mentioning the awesome boss fight that ensues.
Being that he is a typical Non-Human Sidekick with a squeaky voice, unbearably bright demeanor and looking like a demented Moogle, seeing Mieu getting kicked and/or told to shut up can be quite a moment to the jaded JRPG player.
Can we add the final confrontation with the Big Bad to the list? It's just too awesome (and funny) to watch everyone in your party verbally own him, pickingripping apart the Big Bad's logic piece by piece and throwing it in his face.
What makes it even more awesome is you physically backing that up (provided if your chosen party is leveled up and well equipped enough of course). If you succeed with Luke and Tear in your party, you get a final round with infinite HP and TP where you can use any attack and combo you have on Van as much as you want until you trigger Luke's Mystic Arte, Radiant Howl, to end it.
The cameo team battle in The Arena against Reid, Mint, Philia, and Nanaly makes for easily one of the best fights in the entire game.
Best fight in the entire game nothing. A full four on four battle with what could be a fully functional and deadly adventuring team were they in the players hands was the best fight in the series.
Even though it can turn the tide of the battle and potentially wipe your party, Reid's Aurora Wall is very impressive. Equally awesome is the Theme Music Power-Up when a remix of Eternal Mind plays after Aurora Wall.
Reid: We will not LOSE!
During the final confrontation with the main villain, if you don't have Luke or Tear in the active party, whoever you control will have a unique speech once the boss loses a certain amount of health. Arguably Jade gets the best one.
Jade: I don't care about fate...miracles...faith...any of that. I care only about putting an end to what I began. That is why I will take back fomicry. [...] At least I can use it more effectively than you. [...] The fact that I didn't kill you is a sign my skills have dulled. [...] Once we strike you down, Luke and Tear will free Lorelei! Rest in peace!!
Anytime Ion shows that just because he looks like a kid, he's still the Fon Master and he will be listened to.