I'm bored and I like Sheik in many ways... NO, not like that, pervert. I love that her Down Smash is a breakdance, her little hops for her walk is cute, and I just like the way her moves are just so fluid like her Ftilt, Dtilt, Uair, Bair, etc.; she's graceful.
It's weird how I pick my characters. I like Sheik sole-y because of her moves, especially her Down Smash, Ike's part of my younger days of thinking two-handed swords are awesome, Luigi and Link are childhood characters, Yoshi replaced Ike in Brawl for some reason after I went back to Brawl once, Wolf's well, a wolf and I like wolves, Toon Link grew on me because of his speedier play-style, Sonic's back throw is so funny that I use him just to mess with people, I like foxes, so I like Fox except his voice in SSB4 and he was my crutch character - he feels way heavier in SSB4 -, Captain Falcon's over the top, so he's just fun to play as and landing Falcon Punches, Knees, and Nipple spikes are fun, and Ganondorf's well, come on, he hits like a freaking truck, who doesn't think that's hilarious? Oh, and Luci's well, Luci.
Snake and Falco are the only characters I chose to play out more "reasonable" reasons. I like the Metal Gear series and since this is the only fighting game I know/own that has Snake in it, then he gets played a lot. Oh, and explosives are fun. Falco is more of a SSB4 thing since he's being **** on so much, that it ****** me off. I don't think any character has been **** on like this. People complain about Brawl Ganondorf and Captain Falcon, Melee Kirby, and Zelda being bad, Lucina and Dark Pit being clones, or are angry about SSB4 Diddy and Brawl Meta Knight being OP, but then you have SSB4 Falco who's treated like absolute crap because he's not Brawl or Melee Falco. Well, nobody is since each game has fighters being different. You can't play Link like he was in Melee in Brawl or play as Melee Mario in SSB4. So, I just picked him up out of curiosity and because I sort of wanted to prove that he's not a POS character. You want a POS character, go play as Ganondorf in Brawl who has his own separate tier.
Samus, (Dark) Pit, Zelda, Mega Man, Shulk, Dr. Mario, Meta Knight, and Peach are more curiosity characters. They interest me, I like their move sets, or I just don't like something else about them. For one, Mario's Fireballs < Dr. Mario's Pills. Why? Who does not want to OD people to death? Samus? Finally, fina-freaking-ly she has an updated appearance. Holy crap, it's been 4 freaking games for her to get an updated appearance while everyone already had updates.
Edit: For all intents and purposes: I usually have a main or a character I tend to play the most or am attached to the most per game. SSB4 Falco's the only one who I picked out of wanting to prove something and because he's challenging to play as compared to picking Dr. Mario and going to town on people.