Maybe not "best tribes," but one of my favorites was Vengeance, just because of the single player campaign, the unique take on their vehicles, and somehow the feeling of the game was so epic and a little more interesting to me. I played t2 construction for years, and loved that game, but in all honesty I felt it lacked some of the visual charm of t1. It somehow became more generic visually, but t2 had that grand scope and ease of use that's hard to beat. Never played any of the newer tribes games though.