One that hasn't been in previous games
Fresh off of revealing its pricing scheme and initial launch fighter counter, the folks over at Double Helix have revealed a brand new female character for the new Killer Instinct. Although speculation was abound that she may have been popular Killer Instinct fighter B. Orchid in disguise, it seems as if she's a brand new character named Sadira.
Not much is known from the initial reveal trailer, but it seems like she has spider-like qualities of some sort, including web based projectiles. Based on the brief video she's a pretty intriguing addition, and I hope the rest of the game follows suit.
Sadira [Killer Instinct Central]