Trinisphere. A card made by the devil, forged in Hell, and played by only the most evil of players. Last time I played against one, I performed an exorcism, and as he screamed, his deck caught fire, and the unharmed Trinisphere was sucked into the earth. The player was hospitalized, but no cute cuddly animals were harmed. Lesson? Don't play Trinisphere.
Added Etherium Sculptor... cause everyone likes cheaper artifacts. I would also like to say I don't like Visions because its only three cards. What about Scroll Rack or, I hate to say it, Mind's Eye. But I leave my contribution to one card so others may participate.