So I've got some more ideas:

Crusades (again) 

Roles: Knights, male characters only.
It really isn't a romance so, no pairings really.

Basic idea: Life while waging a 'holy' war.

^I'd love to try this one.

-

Queen X King (either married or of opposing countries/kingdoms)
Guard X Royalty 
Poor X Rich
Assassin/ Hitman X Civilian 
Gods X Goddesses 
Cowboy X Cowboy (MxM)
Soldier X Civilian (Historical, set during American Revolution so Loyalist or Patriot characters)

I double, that doesn't mean that you have to either but I still ask you do side characters as well. Oh and either of these, except the cowboy idea (As I'd like to keep it MxM) can go MxM, MxF, or FxF. I'm comfortable with either, and I will still double in some way.