Fighter or Barb, unless you want to start mage because you can find some basic charms for mage. But I would advise a melee char first, because your going to have to experience what to do in hc first; ie] running, grinding, using what you have, etc. So a melee will be the best char because you'll have a less chance of dieing and you can grind a good amount of time with them. If you don't know the fighter guides its here:
http://forums.d2jsp.org/index.php?showtopic=17997568&f=272 , pretty much the same cept you do need 110 - 120 dex for the less crits. Vit should be fine, but you can always put first 5 or 10 to vit just for that extra carefulness ^^