Llanowar Sentinel
Weatherlight — common
Creature — Elf
Llanowar Sentinel rulings:
2007-07-15: Llanowar Sentinels can “chain”: If you put a second Llanowar Sentinel onto the battlefield as a result of this ability, that creature’s enters-the-battlefield ability triggers and allows you to search for yet another Llanowar Sentinel.
2004-10-04: Because the “search” requires you to find a card with certain characteristics, you don’t have to find the card if you don’t want to.