I don't know why, but I think Derpy would be a class that would use heavy weapons.
If we are talking about the class-making of FPS's like Call of Duty or Battlefield, I choose anything I want since I can customize every single thing. If we talk about TF2, I play withwhat fits my style, so I choose whatever I want. Piece of cake.
I hope somepony makes a Splatoon game with MLP. You have things you do in shooters like Battlefield but apropiate and able for kids to play. Yeah, I don't mind the Fallout: Equestria game and wouldn't mind a "Trotting Dead" game either, but kids are the thing that bought us the show. If they wouldn't be, Hasbro wouldn't have made the show for them.