Hmm, some of these are good choices, but where's the obscure references, people? How about these?
Mr. Stevenson (Gumshoe) -- Um... well, actually, even though he's the main character, all he does is avoid obstacles by jumping. No good. Pretty obscure though, huh?
Thomas (Kung Fu) -- Good ol' martial arts combo works well enough.
Professor Hector (Gyromite/Stack-Up) -- He could set up us the b-- er, set dynamite on the stage.
Bubbles (Clu Clu Land) -- Could trap an opponent in her trademark bubble.
Mike Jones (Startropics) -- He has lots of different inventory items he could use, but I'm gonna go with the Snowman to freeze the opponent. Would last longer than a Freezie.
Centurions (Kid Icarus) -- Remember how, when you free these guys, they assist you later? Yeah, they could fire a volley of arrows!
Hikari & Donbe (Shin Oni Ga Shima) -- Yeah, I don't know what they could do. But they had a cameo in Kirby's Dream Land 3, so Sakurai must have some love for 'em.
Chamu & Goku (Yuu Yuu Ki) -- From the same series as Shin Oni Ga Shima, except about the Saiyuki/Monkey King story. Also made a cameo in Kirby's Dream Land 3.
Ice Hockey Team (Ice Hockey) -- The fat guy skates by and body checks the opponent before delivering a slapshot!
Balloon Fighter (Balloon Fight) -- Hmm. Picks up the opponent and tries to carry them off the stage?
Chalvo (Bound High/Chalvo 55) -- WOW. Now THIS is what I call obscure! Chalvo is a character fortunate enough to be revived after his original game (on the Virtual Boy) was cancelled. He's a red robot, and his method of attack involves rolling into a ball and bouncing around at high speed.
Tamagon (Devil World) -- Cut his trophy from the non-Japanese versions, will they?! Well, let's see them cut him when that trophy springs to action! He'd breathe fire, naturally.
Gamma Raiders (Radar Scope) -- You know your game is bad when the company recalls the arcade cabinets in order to use them for a better game (in this case, Donkey Kong). Ah well. Gamma Raiders were your basic space-shooter badguys, decending in waves and firing green plasma at you.
Prince Sable (Kaeru no Tame ni Kane wa Naru) -- He's a young fencer who can transform into either a frog or a snake. So that's kinda different.