Haunted Plate Mail (M14) from Magic 2014, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Izzy
• Card Text:
  Equipped creature gets +4/+4.
  0: Until end of turn, Haunted Plate Mail becomes a 4/4 Spirit artifact creature that's no longer an Equipment. Activate this ability only if you control no creatures.
  Equip 4 (4: Attach to target creature you control. Equip only as a sorcery.)