Fushigi Yuugi OVA 2 when Hotohori possesses his baby son to fight off a monster. Epic.
After being rescued an absurd number of times from every danger imaginable, Miaka from Fushigi Yuugi actually saves her seven protectors from Soi by catching a massive lightning blast in a holy sword and hurling the energy back at the enemy.
Tasuki earned a lot of fan love during the Kodoku arc, in which Tamahome is brainwashed into attacking Miaka. Tasuki arrives just in time to defend her, but as the fight begins, Miaka begs him not to endanger Tamahome's life. Tasuki therefore puts his weapon away, willingly disadvantaging himself, and receives a savage, merciless beating from Tamahome as a result. Even as he grows progressively more broken and bloodied, and even when the absurdly powerful Nakago shows up, Tasuki continues to hurl himself into battle against both men, willing to commit a You Shall Not Pass sacrifice in order for Chichiri and Miaka to escape. Since he'd previously been depicted somewhere between Boisterous Bruiser and Loveable Rogue, this act of pure self-sacrifice was somewhat unexpected (and therefore particularly awesome).
Later in the series, Tasuki has a lesser, but still Awesome moment after Yui has summoned Seiryuu, the Suzaku warriors' powers have been sealed away, and Kutou has invaded Konan. Nakago is in full Evil Gloating mode, the main characters Miaka and Tamahome are in chaos, and out of nowhere Tasuki pulls a Talk to the Fist moment by deciding to simply pick up a sword and hurl it at Nakago's face. In a bit of morbid hilarity, when Soi takes it instead, Tasuki's primary reaction is "rats, I missed."
Miaka telling Yui that she is going to yell at her about many things by the time her battle with Nakago is over.
I find this to be Miaka's greatest revenge on Yui.
Miaka has a subtle but beautiful one very early: when she starts gaining Nuriko's respect and collaboration. Up until then Miaka had acted as if she was Nuriko's maid to try getting into his favors, and due to jealousy he kept treating her like shit — ultimately sending her to seek for a supposedly lost earring in hopes to make her look bad. Well, Miaka obviously doesn't find said earring — she returns with her hands empty, overhears Nuriko gloating about what he had done... then she steps in, slaps Nuriko across the face and loudly calls him out for being selfish, before offering him a pretty and shiny pebble that she did find around. That's quite the Humble Pie eating moment for Nuriko, who breaks down crying due to the humiliation, and from then on acts still snarky but much closer to the cheerful Boisterous Bruiser we know and love.
How about the way Tamahome killed Nakago? You know, by punting a hole through his chest WITH HIS LASER FISTS?! I wasn't even a big fan of Tamahome, but even I had to admit awesomeness when I saw it.