vanilla civ:
queen lizzy- mostly for the redcoats. financial trait is always nice. historically, liz did amazing things for the english empire(more significant and decisive than victoria), woman or not.
qin emperor - 'cause mao sucks, and i don't like his mad interpretation of commie-ism. but i stopped using this guy after i decided catapults and axemen were more efficient than zhuge-nus.
alex- 'cause the man almost could have conquered the world before he hit his 50s. the phalanx are cheap, so pikemen become irrelevant. annoying thing is, i always find elephants when i play as alex , so i end up only using my phals for hill defence.
i had my best cultural victory using mansa musa, but i have a thing against religion... and his skirmishers are only good for defending.
i might use kublai khan again. genghis' expansive trait didn't seem to complement aggressive well. their UU is very effective on rocky maps. anywhere else and they're only good for picking off annoying barbarians and pillagers.