Once you get the Rhythm Badge with Tails in the ancient place, you can hold the attack button to continuously spin around while moving, making Tails invincible and damaging enemies.
IMPORTANT-----Tails can still be hit by projectile, or ranged, attacks, such as gunshots. I am not sure if this will work on bosses because they usually have a specific way to beat them.
NOTE-----I think Amy can spin her hammer for a short while, making her the same as Tails, except for the fact that she gets dizzy and is unable to move for about 5 seconds when this happens.
Added by: lilrayo92 Apr 14th 2006, ID#853