for serious or tough matches:
Spain, Americans, China
for fun:
pretty much random civs are fun. The Indians are the most unique to me, but I do enjoy trying to win with the worst civs like Russia, France, and Mongols.
*message deleted, off topic*
Woah, you actually PLAY rev...
Most popular answer - FRENCH. I love it!
most be a lot of sinlge player posters on this board, because almost no one uses the French online. And for good reason, they are awful.