Now, I use every character on the roster;
But for tournament and ranking as a 'main'?
1.) Zero Suit Samus.
2.) Wario.
3.) Peach.
4.) Captain Falcon.
Zero Suit Samus, of course I shouldn't need to go into details on since this IS the ZSS boards. You should all know her flaws, advantages, problems and play styles.
Wario, as a back-up character, I chose to pick a top tier main that doesn't necessarily have the greatest potential of the roster. He has many grab release flaws and things that could spell bad news for him. However, he has the best air mobility, spacing potential and DI in the game. His aerials are very decent, his smash attacks kill very easily and hes a tough competitor with his considerable priority wall.
Peach, another good character. Where ZSS lacks, Peach usually excels with her projectile and air game. She has one of the best grabs in the game, which she can lock fastfall characters with up to about... 40%, I believe it is. Characters that she cannot, start up a grab, down throw, ftilt a few times and uair. Works just as well. Peach is all about mindgames, so I abuse her wavedash ability to cancel out a constant back air wall to negate projectiles and do a moderate lock to most of the roster at low percentages.
Captain Falcon, pure manliness. Second fastest character in the game with garbage potential. Where he's considered one of the worst characters, I find him to be one of the best in a lot of match-ups ZSS has difficulty with. Regardless of the lack of hitstun, Falcon still supports a lot of legit combos that involve his Fastfall NAIR. His aerial game really isn't all that horrible either if you know how to use fastfalling efficiently. So yeah, I do support Captain Falcon to great extents.