Child of Gaea
Urza's Saga — rare
Creature — Elemental
Child of Gaea rulings:
2009-10-01: If you do choose not to pay, but no longer control Child of Gaea, you cannot sacrifice. It will remain on the battlefield under its current controller’s control.
2004-10-04: You choose whether to pay or not on resolution. If not, then you sacrifice Child of Gaea. You can choose to not pay even if you no longer control Child of Gaea on resolution.