And here we are, after 2 nights in the making with a horrendous sleeping pattern!
Little Pip from the truly excellent Fallout: Equestria series, one of the greatest pieces of fanfiction I have ever read.
Edit: Fixed some minor stuff that was bugging me. Also my reasoning for Little Macintosh being so big is that in comparison to most mares, Li'l Pip is pretty dimunitive, also, despite being called Little.. I'd imagine it'd still be one hell of a hoof-cannon indeed.
MLP:FIM belongs to Hasbro
Li'l Pip & Fallout Equestria belongs to KKat