Brawl's one of my favorite group games, aside from Marioparty - one of the few that I can get a couple of people around here to play. For me, Bowser fits my style fairly well - I love to run in and pummel things, though Bowser's speed leaves much to be desired for the running department. I just love chasing people around as Giga Bowser, though
Though falling through a hole can end that real quick if you get too focused on your targets... Grr Green Hill and your collapsing floor section...
Other than him, I tend to play as either Meta Knight or (if I'm feeling really cheap) Pikachu, with the occasional Fox thrown in. As with almost everything, I rely fairly heavily on luck when I play, since I don't have that much in the way of skills.