Warrior's always been my default go-to to come to grips with the game's mechanics, but I generally find myself creating a new, differently-focused character after a few hours of play, once I'm more comfortable with things.
One rare exception to this for me has been in Dark Souls. I started out Warrior, and while I'm primarily a melee-focused character, melee is actually damn fun in this game for me. I won't be changing this character any time soon-- and I've dumped a ton of hours in with him already.
It's got to be the first RPG-styled game I've played in a while where a strong defensive melee is so much fun to play. I feel actively involved in my defensive offense at all times, be it blocking or dodging, parrying/riposting following attacks, or finding the weak side of the thing in front of me. This game's combat system is brilliant, even in its basic simplicity. So much fun.