I recommend Fox, Yoshi, PT, Shiek/Zelda, GnW, and MK.
Fox can reflector-stall in the lower corners to dodge Off Waves (RROD), moves incredibly quickly which helps dodge attacks, can use Laser to attack from afar which helps protect against that electrical attack, the rain of bullets thing, and others.
Yoshi has eggs and dair, along with the super armor in his second jump.
PT's Charizard has Rock Smash, Ivysaur has Bullet Seed, and Squirtle has nice aerials, which deal damage effectively, and apparently a well-timed down-B can dodge Off Waves.
Zelda/Shiek: See PT. They're weaker.
Game and Watch's nair and bair should do decent damage, he's relatively agile in the air and the uB is pretty nice I guess.
MK is MK. He can stall in the lower corners much like Fox, but trades the projectile for things like Tornado and insane recovery (though Tabuu mostly gets his kills from one-shot Off Waves/bracket throw/telexplode/etc.). Also, a guy did Boss Battles on Insane spamming MK's Nair and took no damage. Apparently.
Sonic, FE characters, Pit, and Toon Link are also all very effective and should probably replace GnW or Z/S on the list, but whatever.