Link/young Link, Samus, and Mario/Dr.Mario
Favourite levels: Corneria, Hyrule Temple, and final destination.
Gotta love:
Corneria because it is big, wide, and has enough special events to keep it going. Always a fun match there! Hyrule temple because its huge, has many places to duck, jump, and run to, and because you can play with really good strategy there. Final destination because its a fair match, where players can't trick or fool you. You can only win there by skill, and thats where I jump in when it comes to SSBM.
I like:
Link/young because he's great in melee and head-to-head. His sword has good reach and is quite powerfull. His bombs are handy when somebody is trapped in a small distant place. Bow is great when you wanna shoot from a safe distant place. And the boomerang kicks ass when you want to shoot a powerfull weapon from a small distance.
Samus because of her balanced jumping/running/attacking, and because of her superior missiles. Charge beam is a great suprise attack, and bombs.....well, they're kinda useless. If you're in a melee fight, and want to go to a platform above, use screw attack for a quick strong jump.
Mario purely because he's totally balanced, and can avoid and reflect nearly every attack. Fireball is best used when in the air, and the up+B jump rocks when you are platforming to platforms with enemies on it. The Mario tornado is a great savior when you are slightly out of reach from the cliff. Of course, we still have Mario's cape. Its great when you want to make a gap in the enemy defense to do your fire smash attack. It also functions great in returning to the safe grounds. Use cape and you'll gain a bit more height when in the air.