Another fun "overpowered" alternative I tried once was to change the barbs' mounted units to 6/2/3 elephants and set them on raging. Once I hit the first barb surge (about 1000bc, IIRC) it was sheer chaos, watching them plow through all the civs on the board. I don't think they actually wiped any civs out of the game, but the damage wasn't pretty to look at.
I forget who I was playing, but if I ever do that again I'll be sure to pick Greece or Carthage (speaking of overpowered UUs).
