Since someone has suggested Bull Cavalry just recently, I am going with a sugestion first mooted in the ASB forum (as part of a shared worlds game). Suppose mammoths did not become extinct and managed to survive the end of the Ice Age, in some frozen polar/tundra region in the far north. What chances might you see of their being domesticated in the way elephants are, what might they be used for if so, and hypothetically, could one "do a Hannibal" with them? What are the possible drawbacks to this? (Size, possibilities of social groupings, differences in culture in mammoth areas, shape of tusks even?)