mtg exile the top card of your library Plargg and Nassari [March Machine: The Aftermath] Search the City

I might be willing to call it a tie for number one, because Shelob is a blowout

It can be pulled off in Constructed in a strong control shell and I am sure it's a really awesome move in Commander

Any deck running two colors or more has basically no reason not to include it, since it provides perfect fixing with no drawbacks

The final room of The Undercity is a pretty huge swing, but introducing the initiative into a game where you're unable to defend it is a losing proposition

The One Ring is a key artifact from Tolkiens world of Middle-earth and an all-powerful unique item

You see, whenever you cast an instant or a sorcery spell, you can have the Dragon deal two damage to any target at all