Ok. First off, Bathory. The first four albums are just ****ing great. Under The Sign Of The Black Mark \m/

Okay, what do Celtic Frost have to do with Black Metal, they were a thrash/death band but never black metal. Oh and avant-garde but...

Arcturus, everything theyr released are great...especially their later material.

Finntroll, they are folk/black metal. It really isn't about what you consider them to be actually, rather what they play. And well the play folk/black metal. With POLKA INFLUENCES! \M/

As for Helloween being happiest, no. Not a chance. Happiest goes to Dragonforce or Sonata Arctica.
You've never heard Bm bands point to "the mighty Frost" as one of their influences? They do it all the time, that's why I brought it up (or at least I thought they did). I was just mentioning that I hear no similarity between the thrash mastery or avant garde experimentalism of Celtic Frost and the minimalistic static cocaphony (sounds like it was recorded on an answering machine) of most Black Metal, although there apperently is one.