Kongo, but only if they get the Mokele-mbembe as a unqiue unit.
Seriously (as cool as the above would be), it would also maybe get a bonus for marshes or jungles, which would be nice.
I doubt we're going to get a cryptid animal as a UU![]()
I want both, don't make me choose.
The Zulu can preserve a spearman-based military into the Renaissance via UU, along with a UA that makes warmongering easier (possibly reduced maintenance costs and bonus starting experience, to reflect the organizational and training advances which were key to Shaka's success).
The Kongo can get bonuses from jungle tiles and a jungle start bias to reflect the terrain of their homeland. This alone would make them a very interesting civ and set them aside; they could have a relatively generic UU/UB (UB is dangerous, as the most natural fit for a Kingdom of Kongo civ is probably some kind of slave market...).
Rivers don't go through tiles.