I play bullet every now and then and come across the fried liver a lot. I know about the defense where you sacrifice your bishop, but does anyone have any other defenses?
You could always avoid it by simply playing Bc5 instead of Nf6, but if you insist on the Two Knights Defense, 5… Na5 (the Polerio Defense) or Nd4 (the Fritz Variation) work decently. Nd4 only works if your opponent is somewhat unfamiliar with it, and Na5 (the main line) gambits a pawn, albeit for a strong attack.