From the Super Mario Wiki
The Homing Attack is one of Sonic's moves appearing in most games in his series since Sonic Adventure. In the Super Smash Bros. series, the Homing Attack is Sonic's neutral special move. When used, Sonic curls up into a ball and hovers in the air before charging down and forward, hitting any nearby opponents. The player can also have Sonic immediately charge forward by pressing the special attack button again, though the move is weaker as a result. The Homing Attack causes Sonic to bounce off of the opponents if it hits, in addition to walls and the ground if it misses.
In Super Smash Bros. for Nintendo 3DS / Wii U, the Homing Attack is given two custom variants. The first is Stomp, another move from the Sonic the Hedgehog series that causes Sonic to slam directly downward into opponents and meteor smash them. The second move is Surprise Attack, which is faster, but Sonic stays in place while charging and the attack sends Sonic into the air a little, giving the move less range.