I've got to go with Passai Dai (Matsumura). I think it's one of the more well rounded kata including strikes, locks, escapes, throws, etc. If I'm going to study only one kata as my style, it should be versatile.

I like Seipa or Superinpa, and Tensho.

Maybe Baisai or Tekki II pending my mood.

Who gives a damn if it looks good? Katas are for kicking ass not for show! The fact that some katas are beautiful to watch is secondary to their bunkai. I would rather have an ugly techniqe that utilizes propper body mechanics for maximum delivery of force and leverage that a pretty one with no power or the with an illusion of power. Just my thoughts.

I believe if a kata is done right it does look good.No excuses for sloppy kata,so I guess I care.

Heian Godan.

And I have been practiscing karate for twelve years. Yep.

I have always liked this kata, and it's rich applications.

Also, I won't be stuffed after perfroming it a few times!

For the kata with the most and/or most important principles it would have to be Naihanchi.

I would have to cheat slightly and take Naihanchi I II and III as one kata.

I've got a feeling I should be picking a Tekki kata here from what I've heard about Naihanchi's applications. But as I havn't got around to looking at the bunkai for myself yet (currently thinking about Bassai Dai) I would pick Unsu as it contains an interesting range of techniques, is difficult to perform so would be physically testing and it's got ippon nukite so I get to poke peoples eyes out. Mind you,it's a kata I never got that good at.