Ice Key

The Ice Key is one of the items that were gonna be used in the mysterious Stop 'n' Swop feature. It appears to be a key made of ice.

In Banjo-Kazooie
In Banjo-Kazooie, the ice key can be found in Wozza's cave, behind a ice wall. The only way to get it is by doing the levitation code.

In Banjo-Tooie
In Banjo-Tooie, you can get the ice key without cheat codes. The ice key is located in Jinjo Village inside a BK Game Pak. After you get the key, you can get the mega glowbo in Glitter Gulch Mine, and give it to Humba Wumba in Pine Grove. It will transform Kazooie into a dragon.