There's a distinct lack of first person shooters in the pony fandom, and for good reason: colourful horses just aren't as fun when you can't see the ones you're playing as. However, that hasn't stopped Jach (you might be familiar with some of his previous works, such as A World You Should Not Know), who decided to switch from the Blender Game Engine to Unity3D and make a game about shooting changelings with guns, because apparently magic missiles aren't good enough for some reason. Players also have the choice of playing as Princess Celestia, Luna, Cadance and Shining Armor, each with their own weapons and magical abilities, which offers some more variety I guess.

 No word on when the project will eventually be released, although Jach claims he'll set up a blog for it in the near future with development updates.
This was the closest thing to a SFW Princess Shining Armor picture that I could find.