“Lucky you! I'm an invulnerability feather! Bottles will tell you more...”
—A Golden Feather, Banjo-Kazooie
Golden Feathers, also referred to as Invulnerability Feathers, are used to perform the Wonderwing ability. Each Golden Feather allows Banjo and Kazooie two seconds of almost-complete invulnerability. Golden Feathers are quite rare, usually being found in no more than pairs. Kazooie can only carry 10 of them (or 20 when Banjo finds Cheato and types in GOLDFEATHERS on the Treasure Trove Cove) equating to 20 seconds of Wonderwing time (or 40). The initial amount is 25 in Banjo-Kazooie: Grunty's Revenge.
In Banjo-Pilot, the Gold Feather is an item that can be obtained by racers in 7th or 8th place. As expected, it makes the user temporarily invernerable, which renders them immune to attacks, provides a small speed boost, and allows them to wipe out opponents by crashing into them.