Culling Scales

Oracle Text

At the beginning of your upkeep, destroy target nonland permanent with the lowest converted mana cost. (If two or more permanents are tied for lowest cost, target any one of them.)

Card Rulings

12/1/2004 You choose the target. If there’s more than one nonland permanent tied for lowest converted mana cost, you choose which one to target.
12/1/2004 If the targeted permanent doesn’t have the lowest converted mana cost when the ability resolves, the ability doesn’t resolve and the permanent isn’t destroyed.
12/1/2004 Most tokens have a converted mana cost of 0. A token that’s a copy of another permanent or card has a converted mana cost equal to that permanent or card’s converted mana cost.
12/1/2004 If the lowest converted mana cost is 3, Culling Scales can destroy itself.