You're talking about Toushiro Hitsugaya. His techniques are one of my favorites also. Ichigo's Bankai is awesome too, but I have a feeling that we will se a bit often. I'm interested to to see what Urahara's Bankai looks like because I know he's reached his.
Sealed Sword Frenzy was pretty tight. I think that guy, what was his name, Baishin I think he had a bad ass Bankai too. That was a very dangerous man. He must've went insane after he somehow fused with his Zanpakutou.