Project S.T.E.A.M. Strike Team Eliminating the Alien Menace has been trademarked by Nintendo, and has absolutely nothing to do with Valve's digital marketplace.
The title was filed in the US on April 2, and pertains to the usual list of, "Cartridges and memory cards featuring video games; downloadable multimedia files, namely, video games; downloadable electronic game programs; downloadable electronic game software; electronic game programs; electronic game software; video game cartridges; video game memory cards; video game programs; video game software."
We've no idea what it is, but some sort of sci-fi shooter wouldn't be a bad guess.
We'll have more as it comes.