GS Ball

The GS Ball is a special and mysterious Poké Ball. It is colored gold and silver and has the letters "GS" inscribed upon it.

In the anime, Professor Oak was studying it, but couldn't figure out how to open it or transmit it via PC. So Professor Oak asked Ash to take it to the Orange Archipelago and give it to Professor Ivy to study. This prompted Ash's participation in the Orange League.

When Professor Ivy couldn't do anything with it, Ash was once again asked to deliver it to Kurt, a Poké Ball researcher and manufacturer living in Johto's Azalea Town. It still resides there to this day, and it seems we may never know it's purpose in the anime.

In Pokémon Crystal, players could use the mobile phone system to gain a GS Ball that they could take to Illex Forest. Using it at the forest's shrine would prompt an encounter where a wild Celebi could be captured.

In the Pokémon Special manga, the GS Ball was created by the Mask of Ice - using the feathers of Lugia and Ho-Oh - to capture Celebi. Only the feathers of the two Legendary Pokémon could contain Celebi, and prevent their holder from suffering the ill effects of time travel. Gold was able to use his Pichu to destroy it and set Celebi free.