Prizes that can be found only by digging

To encourage digging, I thought it might be nice to offer more goodies that can only be found by digging. There are a few already, but I think we should add some more. Since they are powerful items, they'd be very rare. A few suggestions:

1) A "superport" card. It would be a teleport card that can only be used once but allows you to pick exactly where you want to teleport to.

2) Membership upgrade cards. Find this special card and get upgraded status for 3-5 days. As a bonus, once people understand how great subcriber benefits are, they might subscribe on a permanent basis.

3) A homestead protection card. Find this card and your homestead will be invisible for 24 hours. No one will be able to attack you.

Any other suggestions?

Mike