I have been getting a lot of ideas in my head, some sound pretty awesome, others 'been there done that' and a few sound more 'hit and miss'
My ideas are as stated:
A Undead Pirate Hunter who is dragged to Equestria and despite hate for the Princesses of dragging him to this new world, he will still do his job of capturing pirates
A Warhammer idea of Tyranids and/or Chaos coming to destroy Equestria
A Warhammer idea of Eldar and Guardsmen protecting the ponies from a Tyranid swarm