I reckon a Total War game called Total War: Timelords would be good. You play as a small tribe any where in the world and can go right into the futre. (Did i spell futre right?)
Possible weapons/units:
Right from the start you could have men with bones or spikes attached to thier fists(sorta like stone age knukledusters!)
When you get to say 2150 you can have cyanide bullet guns: as soon as they pierce the skin they release cyanide, so even if the bullet misses the one hit kill area(head,neck,heart,lungs,etc.) theyll still kill the guy!

What do you think?