These are the people I play as and the reasons as well:
Lucario: He is my initial first choice. He has adequate speed and nice counters. Although he does not have a Wall of Pain, he has a nice [Neutral B] that gets better as he sustains more damage. His Final Smash is a little bit on the weak side, but does some good if you aim at those that have high percentages; one attack from Lucario's Final Smash will send them flying. Although he is better for those who play better the more damage they take (Characters gain an increase in attack power the more damage they sustain, f.y.i), he can be good for those who want to experiment with different people. The main color I use for him are his original colors and his white form.
Meta Knight: My second choice. If I don't want Lucario, I immediately go to Meta Knight. In my opinion, he has the best Wall of Pain on the game. The flaming tornado (Neutral B) is a great way to start off air combos. Simply take them to the air, let them fall, they do an [Up+B] to knock them off. He is slow, but has no lag in his attacks (that means I can do the same attack over and over again without a break in between attacks like other characters). His Final Smash is only good if you can get an opponent to touch the cape. One time, I got everyone I was playing against touching the cape, giving me +3 points. Sweet. Anyway, His Final Smash is also very cool looking. The main color I use for him is his white form.
Sonic: My third choice is none other than the fastest thing alive. Sonic is literally the fastest character on the game with little lag in between attacks like Meta Knight. Because of his speed, he is hard to control sometimes, but you have to get used to that in order to utilize him effectively. He also has a good recover tactic (Down+B). You can use this to gain some nice height, however it leaves you wide open for air combos. Sonic also has, in my opinion, the second coolest and third best Final Smash in the game (Meta Knight has the coolest; Link and Toon Link have the best Final Smash, wheras Bowser has the second best). Being SUper Sonic is a great thrill, however he is hard to control in the air. He inflicts some decent damage with his Final Smash and can send an opponent flying in three to five hits. The main color I use for him is his dark blue with the black bands.
Kirby: Last but definitely not least, Kirby is a threat on the field. He is notably slow, even when running, but jumps very high and has little lag like Sonic and Meta Knight. His Neutral A is good for picking up some quick damage, followed by a quick [Direction Towards Opponent+B] to knock them off. His [Neutral B] is probably one of the most annoying but useful ones in the game. Inhale your foe and steal their powers; that's how I roll. I prefer to use this tactic on power players like the veterans or the game (However I think it absolutely sucks that you can't steal Kirby's own powers. Just think: Inhale 2 opponents and steal both of their powers...cool). His Final Smash is only good for knocking foes off the stage and picking up some good items. I honestly think it looks stupid. Nonetheless, Kirby is a power player on the field. His recover tactic, along with Sonic, Meta Knight, and King Dedede, is one of the best in the game, able to gain immense height but leaving him wide open for air combos. The main color I use for him is his regular pink self because I get hungry when I use the other ones...>_>
There you have it; the people I use in Brawl and why.