My mains tend to change as I get better in the game, but two characters I have remained consistent with are Sonic and Olimar.
Olimar, I got used to when I first got Brawl. I just really liked his fast smashes and throws. And spiking is fun with the red Pikmin. 8D
Then, about a few months ago, a friend of mine at college kept destroying me and my friends with his Kirby, Lucas, and Pikachu. I decided I needed to get a character that can get in through his spot-dodging and strike back. So, I decide to pick up Sonic. At first, I sucked with him, but after about two weeks of practice, I was able to match up with him, and by the end of the semester, we started trading victories between one another. 3-stock matches would take 10 minutes at a time between us XD So I decided to keep Sonic as a main from then on, and now he has become my true main.