Ascended Meme: Bionic Farm became a minor meme since Applejack's VA for this game said it as a joke at the end of her audition piece. That said, it's now one of the things she says in-game when using Summer Rambo.
Badass Normal: Compared to the rest of the initial roster (even Pinkie, considering that they put Pinkie's cartoonlogic in as teleport moves).
Pinkie Pie: Lookie, lookie! The screen says I won!
Instant Costume Change: Pinkie Pie's launcher has her instantly put on her confetti-shooting saddle and hat from the Party of One episode.
Offscreen Teleportation: Invoked with her "Be Right Back" move and one of her supers. With "Be Right Back", she runs off screen and suddenly appears somewhere else according to the button press. The super version is similar, but is followed by a super-fast combo with onscreen teleportation.
Random Effect Spell: Her Party Cannon can shoot a random item for 1 magic point or one of your choice for 2.
Anthropomorphic Zig Zag: Compared to the rest of the mane 6, she fights much more like a human fighting game character. Her idle animation even has her standing on two legs rather than four.
Furry Reminder: She can only stand on two legs by flapping her wings to balance herself, though, and her crouching idle stance is decidedly non-human (but no less aggressive).
Difficult but Awesome: The developers described Rarity as a very technical character when she was introduced. Rarity's specials involve playing keepaway with the opponent and being as unpredictable as possible, so she takes some practice to execute. With enough of that practice, though, your opponent won't know what to do against her.
Gemstone Assault: Rarity's special attacks and level 1 and 2 super are various gem-based attacks.
Macross Mineral Massacre: Rarity's level one and two supers are firing a hyper-rapid volley of gems upwards from the ground at her opponent.
Attack Animal: Fluttershy's pet rabbit Angel, as well as every other animal in her arsenal.
The Beastmaster: Fluttershy's rabbit Angel will assist her for some of her normal attacks, and the rest of her animal friends act as her special attacks.
Death Glare: Fluttershy's Stare during one of the livestreams is a particularly literal example. It's actual purpose in the final release, however, is to cause an extended period of hitstun to the opponent.