Minecraft's studio, Mojang, has revealed their cancelled game was a first-person shooter. The game was to be a collaboration but was cancelled in the prototype stage. Notch, aka Marcus Persson, says the game was canned because Mojang "did not want more external dependencies." Going forward, Mojang wanted to focus on IPs they owned.
This doesn't mean Mojang has sworn off working on a project with another studio. Mojang said they'd be interested in a collaboration if they were "not to make money. If there are other reasons to collaborate, maybe!"