I'm pretty decent with Roy and Marth on a non-competitive level, but I'd never stand a chance at tourneys. I can't wavedash every single time, nor do I feel the need to practice until I can. It's then that a game loses it's fun for me, so I have no interest in playing any other way than casually.
I usually don't use weapons, but I'm a big favorite of 200% damage battles w/Bomb-Ombs and Motion Sensor battles. Those are a blast, literally.
Really don't have a combo. I suppose you could consider the positioning of Roy/Marth's thrust attacks, but that opens a world of opportunity for other fun chain moves. And it's not a combo, but descending down into the fray while charging up your B attack...that's fun to watch. One word: SCATTER!!!
I also LOVE playing with Ice Climbers, Peach, and Jigglypuff. Jigglypuff especially, since lots of people underestimate her. And Peach is just hilarious. Nothing like hearing the smack of a frying pan

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Meh, I really play decent with just about everyone. Like when we do Tiny Melee, I'm ALWAYS Pichu, just because it's hilarious to watch it run. Yeah, definitely not the greatest character, but my friends play it for the fun factor, not the "I just kicked your ass!" factor.