Do mercs count?
Anyway, besides them, I rank villagers among one of the most powerful human units. Costing only one pop, they beat just about everything pop-wise, and sometimes cost-wise as well. They also have a hefty bonus vs towers that is find quite useful at times.
Shades are also extremely powerful for their pop, as are militia, but those 2 really can't be considered. Unless you delete your temple in archaic as hades, never gather favor the entire game, then rebuild it in Mythic after losing hundreds of units. This is basically a weaker version of ragnorok, I've never did it, or seen an opponent in rated that did it, so I suppose it is no where near worth doing just for a shade spam in late mythic which 5% of rated games actually get to mythic anyway.
Some questions:
1. If you delete a military unit does it have a chance to become a shade?
2. Does a myth unit have a chance to become a shade?
3. Does a killed villager/deleted villager have a chance to become a shade?
4. What about a fishing boat?
5. Hero?
6. Does a shade have a chance to become a shade? (lol)
7. Will any deleted unit be elegible for "shadeship"?
8. If you delete a temple will the shades that were supposed to come out of it stay in "limbo" until you rebuild it? All at once?
9. Will shades come out of your temple if you are at pop cap?
Best game ever made, don't dieeeeeeee