I suck at picking favorites, AND i have too much time on my hands, so I'm just gonna rate them all.
Bowser - Giga Bowser
Awesomeness - 8.0 (Dude, just look at him ._.)
Usefulness - 9.5 (Killing machine.)
Personal Favorite Rating - 4.0 (Yet...I'm not too fond of him as a whole.)
Diddy Kong - Rocketbarrel Barrage
Awesomeness - 7.0 (Pretty awesome. Flying monkeys with airstrikes FTW.)
Usefulness - 7.0 (Bombing your foes from high in the air seems cool enough to me)
Personal Favorite Rating - 7.5 (I like it. Its a great concept)
Donkey Kong - Konga Beat
Awesomeness - 4.0 (He's been doing it for the last five or so games..)
Usefulness - 5.0 (While it may look horrible, I believe its got potential when used right)
Personal Favorite Rating - 3.0 (I don't like it much.)
Fox - Landmaster
Awesomeness - 5.5 (Its not that epic, but it can do a barrel roll!1)
Usefulness - 5.0 (If you can use it, its decent. using it is the problem. its big.)
Personal Favorite Rating - 3.5 (Again, doesn't interest me.)
Ike - Great Aether
Awesomeness - 7.5 (This is awesome. Thats all there is to it. Epic sword maneuver.)
Usefulness - 5.5 (Get close and BAM, headshot.)
Personal Favorite Rating - 7.5 (I like it. If I use Ike, i'll enjoy every minute of it.)
Ice Climbers - Iceberg
Awesomeness - 5.0 (It LOOKS awesome. I mean, they high-five, and BOOM.)
Usefulness - Never seen in action
Personal Favorite Rating - 5.0 (I don't hate it, and its pretty neat.)
King Dedede - Waddle Dee Army
Awesomeness - 4.5 (Its...well...basic.)
Usefulness - Never seen in action
Personal Favorite Rating - 4.0 (...basic...)
Kirby - Cook Kirby
Awesomeness - 5.0 (It works.)
Usefulness - 6.5 (It seems effective, plus free healing items.)
Personal Favorite Rating - 5.0 (Don't love it, don't hate it.)
Link - Triforce Slash
Awesomeness - 7.5 (See Great Aether.)
Usefulness - 6.5 (Horizontal recovery just puts it ahead of GAether)
Personal Favorite Rating - 6.5 (Its cool, it works with Link, and it has the triforce.)
Lucas - PK Starstorm
Awesomeness - 7.5 (Raining psychokinetic meteorites at will? Yes please.
Usefulness - Never seen in action
Personal Favorite Rating - 8.0 (Earthbound love and awesome visuals make it, well, awesome)
Mario - Mario Finale
Awesomeness - 6.0 (Awesome enough to be awesome.)
Usefulness - 6.0 (Works enough to work)
Personal Favorite Rating - 5.5 (Its Mario, what did you expect? Its going to be decent.)
Meta Knight - Galaxia Darkness
Awesomeness - 6.5 (Meta fangirls are going to sue me for making it below 10.)
Usefulness - 7.0 (Really, I'll be calling my lawyer.)
Personal Favorite Rating - 5.0 (...I'm kidding, I'm kidding, no offense to Mety fangirls D: )
Princess Peach - Peach Blossom
Awesomeness - 3.0 (Not very epic.)
Usefulness - 5.5 (It would be more useful if jumping didn't kill it completely.)
Personal Favorite Rating - 3.0 (It doesn't seem horribly good.)
Pikachu - Volt Tackle
Awesomeness - 6.5 (I'm a Pokemon fan, so naturally, I find it pretty awesome.
Usefulness - 7.0 (Pass through stages? Jack damage into the triple digits in seconds?)
Personal Favorite Rating - 5.5 (I like it. It looks cool. And its blue. Blue rocks.)
Olimar - ???
Awesomeness - ??? (it better be awesome)
Usefulness - ??? (it better be useful)
Personal Favorite Rating - ??? (it better NOT be a horribly crappy army attack)
Pit - Palutena's Army
Awesomeness - 6.0 (Its cool that you can do stuff while the FS is going.)
Usefulness - 6.5 (And that includings throwing people into it.)
Personal Favorite Rating - 5.5 (God I hate spelling its name.)
Pokemon Trainer - Triple Finish
Awesomeness - 7.5 (Thats awesome. Everyone just...fires thier lazers.)
Usefulness - 7.0 (Get right up to them and FIRE YOUR LAZARS)
Personal Favorite Rating - 7.0 (He...he FIRES HIS LAZER. Ok, I'll stop now.)
Samus - Zero Lazer
Awesomeness - 7.0 (I'MA FIRIN MAH LAZ...er, sorry,)
Usefulness - 6.5 (Its as basic as it gets. Fire. Boom. Dead. Win.)
Personal Favorite Rating - 6.5 (I don't know what else to say except for another lazer joke.)
Snake - Grenade Launcher
Awesomeness - 6.5 (Its fairly awesome. I mean, you can SHOOT PEOPLE. Fun.)
Usefulness - Never seen in action
Personal Favorite Rating - 6.0 (I wish Snake's butt didn't take up half of the freaking screen.)
Sonic - Super Sonic
Awesomeness - 6.5 (Funfact: This is the first game since Sonic 3 where he can go Super...)
Usefulness - 7.0 (Fly around and kill, kill, KILL, oh its over.)
Personal Favorite Rating - 6.5 (...in an area other then the final boss. Cool, eh?)
Wario - Wario-Man
Awesomeness - 9.5 (I can't think of a caption awesome enough. He's in TIGHTS. I think.)
Usefulness - Never seen it in action...because nobody bothered to use him at JumpFesta >_<
Personal Favorite Rating - 9.0 (This is Wario. Pure, uncensored, Wario brand awesome.)
Yoshi - Super Dragon
Awesomeness - 8.5 (The fact alone its from Super Mario World makes it awesome.)
Usefulness - 8.0 (Free flight? Spew fire on people? Hell yeah.)
Personal Favorite Rating - 7.5 (The awesomeness burns...when Yoshi sics it on you.)
Zamus - Crystal Flash-y thing
Awesomeness - 1.0 (Ugh.)
Usefulness - 0.5 (Ughhhhh.)
Personal Favorite Rating - 0.1 (PLEASE say it isn't as bad as it looks. For Samus' sake.)
Zelda - Holy (s***) Light Arrow-y thing of Death, Destruction, and Rubbing It In Pit's Face
Awesomeness - ??? (I totally made that name up)
Usefulness - ??? (Now that I called it that, its gonna suck)
Personal Favorite Rating - ??? (Whoops.)
...you can tell I got bored halfway through that.
...meh.