The fact that this game is a reality. Fans of BlazBlue can rejoice in finally having a crossover, fans of Persona 4 can rejoice in their favorite characters coming back once again, fans of Under Night In-Birth can rejoice in how it will be put out there, for more fans to get hooked on, and the RWBY FNDM can rejoice in the fact that their favorite characters will be in a fighting game!
The amount of team-ups that can be made, with some badass team possibilities.
The animations. They look AMAZING, especially considering the fact that RWBY started as a 3D franchise. (So did Persona 4, but it did have animated cut-scenes.)
Astral Heats are confirmed as set to make a return for BBTAG, for characters from all four franchises. BlazBlue, Under Night In-Birth and Persona 4 Arena characters carry over their Finishing Move from whatever game they came from, as detailed in theirrespective Awesome pages, while RWBY characters get entirely new ones.
Ruby replicates decapitating the Nevermore from Volume 1, Episode 8, only this time all on her own and in midair, with only Cresent Rose's recoil.
Weiss bombards her opponent with her glyphs before summoning a giant ice sword to finish them off.
Blake slashes opponent into the air before driving them back down into the ground with a spinning slice, with the opponent disolving away after the last strike.
The games main theme, Crossing Fates has four different versions for each of the franchises. Daisuke Isiwatari composed the BlazBlue version, Jeff Williams for RWBY version, Raito for the Under Night In-Birth version, and Atsushi Kitajoh for the Persona 4 Arena version. That's right, they brought in the original composer for each series to mix the song each in their own style.
Ragna and Hyde's team quote.
Ragna: Cut straight through and take em down. You got a problem with that? Hyde: Not at all, that's what I always do!
Ragna and Yu's special intro deserves some recognition too.
Yu: Izanagi! Ragna: Hmph, I guess that's one idea... Yu: Let me work with you. Won't be able to do this otherwise. Ragna: Oh do whatever you want, just don't fall behind. Yu: Then we're a team! Well... Both: Let's go!!
Yu and Hyde make the terms of engagement clear with each other quickly.
Hyde: I don't pull my punches. No promises you won't get caught in the crossfire. Yu: No problem. Don't hold back on my account. Persona!
Normally Ruby's intro dialogue is more hilarious, but she gets a cool moment finishing fellow scythe user Gordeau's Badass Boast:
Gordeau: My Devourer will carve out your spirit. Ruby: And my Crescent Rose will claim our victory! Gordeau: Now let's get this party started.
Ruby sassing Hyde in their special intro:
Hyde: If you're scared, you can just stand back and watch. Ruby: Same to you, Hyde. You don't have to fight if you're scared of me showing you up. Hyde: Roger tha-! W-wait, hold on!
Yu shows off his leadership chops in his intro with Ruby:
Ruby: Our opponents look pretty tough this time, don't they, Narukami? Yu: No worries! [draws his sword] With my Persona and your Semblance combined, no enemy can stand against us!
Gordeau is in disbelief that Yukiko's a fighter:
Gordeau: A pampered lady like you is gonna fight? Are you jokin'? Yukiko: Just watch me and see if I'm joking.
Now that Yang is in the game, you can bring all four of Team RWBY together in a friendly sparring match which gets in a unique four-way battle intro:
Ruby: Helloooo! How's everyone doing?
Blake: Team RWBY is back.
Yang: Alright, let's make this a good one!
Weiss: Then I'll count us down: Three... Two... One...
Just because Hyde and Vatista are going to spare you doesn't mean they aren't about to kick your ass:
Hyde: Guess I've gotta hit you with everything I've got!
Vatista: No worries, I assure you will survive.
Platinum initially underestimates Linne for her size in their shared interaction. Linne, in response, decides to "shut [her] up with skill" and let a century's worth of experience and agility do the talking. If both of them survive the battle, Platinum is shown to be stunned by latter's prowess, a sentiment that continues in their post-battle quotes.
Linne: So, have you got anything to say to me?
Platinum: W-well... You did pretty good, for a pipsqueak! I-I guess I can take pity on you and let you fight with us again.
If you've ever questioned how faithfully Mori can bring Team RWBY to life in a fighting game then rest easy, as someone did the leg work and has shown that many of the girls' attacks were pulled straight from the show and do an excellent job of showing just how much of a fan Mori is of RWBY since even before having the opportunity to have them throw down with the BlazBlue crew.
Death Battle pitted Weiss against Mitsuru in a 3D animated battle, with both combatants putting on a stellar show. Mitsuru wins, as she's canonically tougher than Weiss, can keep up with Weiss' mobility via reaction times and her Persona, can heal any damage Weiss can inflict on her, can resummon her Persona even after a Persona Break via her Evoker (whereas Weiss can't recharge her Aura quickly), and Weiss' ice-based techniques are next-to-useless against Mitsuru.