I'm definitely a leisure player. But I know people who do play in tournaments and I talk semi-often when them. At least, when I can talk with them face-to-face.
As for my favorite characters to use, I used to always use Pichu and Ice Climbers, till I finally came to my senses about how much Pichu sucks. So now I use Pikachu as my main. Why Pichu/Pikachu? 'Cause they're fast, and I love fast characters. Once I get back to the point I was before I lost my memory card (=P), I'll probably re-add Ganondorf to that list, since I did use him regularly way back when. His ability is teh win.
I wouldn't even ATTEMPT a tournament. I'd get my ass handed to me on a silver platter with a little garnish on it. I mean, I'm not even going to try it at Otakon, though I might do some basic playing outside of the tournament itself.