HBS/Longsword. Claymore's my favorite top tier, but I settled with the german my first gen playing.
Honestly though man, don't underestimate the other ones around. Dadao and Miaodao are phenominal swords. Couple people will argue in favor of the 'regular' Great Sword. Pick what looks coolest, or sleekest to you. Half the game is feeling like a badass, and you can get away with using the 1h meat cleaver in this game if you try hard enough.