when you've been grinding for weeks to get magnet reverse for your magnet warriors deck only to realize its crap since you can't use it if you summoned valkyrion with deltas effect.... :
Magnet Reverse - Duelist Pack: Rivals of the Pharaoh - YuGiOh
Amazon.com: Magnet Reverse - SR10-EN028 - Common - 1st Edition : Toys & Games