I know a couple. If cervantes A+B GI's a long horizontal at tip range (like NM or asta 1A), he performs a different move where he teleports into the air quickly and slams a UA attack down on you. Looks F*cking Badass.
Cervy also has another hidden move, where he shoots behind him when he does DC K
Astaroth is the only character with unique dialogue against himself (Death scream sounds more "defeated", different win dialogue).
When Playing as Kilik with Xiba style VS Xiba, Kilik says "YOU LACK, SPIRIT" instead of his usual taunt. Also, shoutouts to YULAC.
Patroklos side throw (the one where he dislocates your elbow with his shield and slams you away), RO's strangly, with your opponent hovering above air for 3 seconds before falling out of the ring.
There are some unused dialogue and intro's outro's in this game that can only be accessed through hex-editing. For example, Yoshi has a"Thou shalt , be slain" line, Cervy has a "Pray to your gods!" line that he says after most other CE's and also a "You got spunk!" XD line he says at other times, like doing WR a+bG as Damp style. Also, setsuka's intro where she walks in twirling the umbrella is still in, I got this intro when I swapped regular patroklos style with aPat on P2 side.
If you do an attack that jumps high into the air and Viola does a CE while the orb is behind you, hilarity ensured.