EF-12 is, basically, a 3-D version of M.U.G.E.N, created by Masahiro Onoguchi, and available for $1.
It's still early days, so there aren't many characters or stages to download yet. It's coming to Steam (via Greenlight), and will incorporate Steam Workshop.
Characters can be made with a number of 3-D modelling programs, include the Blender, which is free.
It will be included in Salty Bet!