Yeah, no offence to Herc, but he has nothing on the Black Knight. Then again, I think that the only F/SN Servant that isn't ultimately inferior to their Zero counterpart is Saber, due to being the same person and all. >.>
...Um... And Archer, I guess. Although Gil is pretty much just classed as "Gilgamesh" in F/SN anyways, so... It still works, I guess.