The best third season of a Trek series? It would have to be TNG. The show really pulled it together during this season, which culminated in the first half of The Best Of Both Worlds.
DS9's third season was a close second, but that series didn't really get good (IMHO) until the fourth season.
The best funny person to hang out with? After giving this some thought, I would have to go with T'pol, too. I recall a really funny moment in Enterprise where she was making one zinger after another (in complete deadpan fashion) with Archer and the others all expressing shock and joy.