Blue Mary is top pick for me hands down. If there is a second wave of DLC characters and she doesn't make it, then I'll have to consider that there may be an actual conspiracy against me.
Others I would like to see include Oswald, Eiji, Rugal (or Adelheid), Shen Woo, and some Garou: MOTW characters would be nice too.
What I really don't want is characters that are too close to characters we already have in the game. That means no Kyo clones (or Shingo, sorry), no shotos (I have mad respect for Takuma, but no thank you). I'm not saying they can't come eventually, but we have so many entirely unique characters that haven't made it yet. Let's get those guys in first.
ABSOLUTELY NO BAO OR MOMOKO! I would honestly pay more not to have them than buy them in a DLC pack for a discount. Hands down worst designs in KOF history (outside of Maximum Impact that is).