My favourite characters tend to be Toon Link, Link, Zelda and Kirby. Kirby is epic, he really is. A combination of suction powers, smashing hammers and throwing punches, Kirby adds up to one of the most powerful characters in the game. Unfortunately for me, my sister nabs Kirby and demands I be someone different -_-. So, I usually go for Toon Link because I prefer him to normal Link. I like his moves too, boomerang, bombs, and the many sword motions. Even though Link also has these moves, I just think Toon Link is cute. Zelda is also a good character, I rarely play as her but when I do I normally win.
Pikachu is a popular choice among my family. When Pikachu gets the smash ball his power is good, some character's need skillfull players to master the smash ball powers, whereas for Pikachu it is fairly easy to knockout everyone. However, I have mastered Link/Toon Link's smash ball power, it's not hard though when you are playing against a 11 and 8 year old! xD
But, unsuprisingly, for me the Zelda characters are superior to the rest.