Gold Shield
From Sonic Retro
The Gold Shield is a power-up exclusive to Sonic 3D: Flickies' Island, and a variant of the standard Shield. In addition to serving as a one-shot barrier against damage and life loss, the Gold Shield allows Sonic to perform what the instruction manual called [1] the "Sonic Blast Attack": a primitive version of the Homing Attack. Double-tapping or
would cause Sonic to jump and home in on a badnik (over a limited range). The shield couldn't be used to execute a Jump Dash, however; if there were no enemies in range, a double-jump would just bring Sonic crashing back to the floor, similar to the Stomp move of later games.