Darth Maul's! Or the Darksaber! Or probably Samuel L. Jackson's lightsaber.
Actually, nevermind. Nothing can beat a lightsaber that doubles as a helicopter.
And because one was to big to post...
But Kylo Ren's is cool too. I personally think lightsabers should resemble our world's swords in that way because it's smart. I saw a Tumblr post that went into detail about that, but I can't find it now. It talked about designs like that, and like the foil, and it would significantly lower the chances of limb loss. And it made Kylo pretty much the only Skywalker not to lose at least one hand.