Hearts of Iron is pretty notorious for it's pony mods at this point. There are extensive ones for the actual Friendship is Magic world, with loads of characters being assigned their own nations. This mod takes that concept and expands it to a post-nuclear Equestria, where various Fallout Equestria groups are vying for power instead.
To check out the mod, head on over here, and a music mod here. More screencaps below.