Debut: Sonic The Hedgehog (1991)
Abilities: Spin Attack
              Spin Dash
             Slow Spin
                   Chaos Wave
                  Chaos Dash

Debut: Sonic The Hedgehog 2 (1992)
Abilities: Spin Attack
              Spin Dash
             Slow Spin
                             Temporary Flight
                   Chaos Shield

(Tails top running speed is 1/3rd slower than Sonic's)

Other (non playable) Characters:

Knuckles The Echidna

 Dr Eggman (aka Dr Robotnik)

Dr Eggman's Badniks.