Ideas
1. A wizard unit or something
2. Cavemen
3.Missiles
4. Submarines
5. Army trucks
6. Knights
7. Army ranks e.g general, captain, lieutnent, corporal
8. Muskets and/or bayonets
9. Elite units
10. banner men/flagmen (carries banners/flags that boosts nearby units)
11. longbow men
12. Vikings (not lord of Vikings)
13. Ninjas
14. Trebuchets
15. wall miners
16. battering rams
17. Terrorrists