Hypocrisy Destroys Wacken is the one where my jaw really drops everytime I hear it. But for studio albums, I guess I'd probably say either Virus or Catch 22 v2. His growls just sound much cleaner and more refined I guess. I love his vocals on the Final Chapter, but I'm just more impressed by his recent vocals.
And that is pretty damn rare. Usually, metal vocalists start off great and then turn to crap in their later albums. Tagtgren and Tomas Lindberg are the two guys who I really prefer their recent work over their earlier work.