Snowman is an enemy Badnik encountered in Diamond Dust Zone, the fourth level of Sonic 3D: Flickies' Island.
A mobile snowman with a snowball cannon embedded in its hat, this Badnik is one of the zone's more dangerous opponents. They slide around on ice-covered floor sections, following unpredictable routes and periodically spewing out snowballs in a half-circle. Sonic must take care and time a Spin Dash or jump tactically to destroy the enemy and make Flickies' Island a slightly less dangerous place. The organic battery power source, a blue Flicky, pops out frozen in a block of ice, which can actually be quite convenient - it stops them wandering off the moment they taste freedom.
The name of this Badnik is conjectural, as no official name has been given to it. The name comes from the level editor in a development build of Sonic 3D that is included as a bonus feature in Sonic 3D: Director's Cut. Jon Burton has confirmed that the name was used in the original game.
While this was the first snowman-themed badnik in the Sonic games, similar robots have followed: