Piston Sledge

Oracle Text

When Piston Sledge enters the battlefield, attach it to target creature you control.

Equipped creature gets +3/+1.

Equip—Sacrifice an artifact.

Card Rulings

6/1/2011 If there are no creatures on the battlefield that Piston Sledge could be attached to when its enters-the-battlefield triggered ability resolves, it remains on the battlefield unattached.
6/1/2011 You can sacrifice Piston Sledge to pay its own equip cost. It won’t become attached as it will be in your graveyard.