First this list won't be long and it will contain 3 categories
Good guys - you know the good guys
Bad guys - the one that fight the good guys
characters with they're own side - you know the cool style characters

Good Guys:

Sonic
Shadow
Tails
Knuckles

Bad Guys:

Light Sonic
Light Shadow (yes the light sides don't work with sonic but they do work with each other)
Tails (secret)
Knuckles(secret)

Characters With They're Own Side:

Dark Sonic
Dark Shadow
Mighty
+
Silver

if someone didn't understand something because they are some things that look weird here please comment but i will pm you back because i don't want to show the answer to everyone