'88 Donruss Gregg Jefferies?
Seriously, though, I agree with those who have stated the sharpest increase will be a card that is relatively inexpensive right now. Perhaps a $20 card goes to $2,000 or some other 100x jump.
Hell, Mike Trout's Topps Update went from about $20 to about $2,000 in about 10 years.
As much as I like other cards in this thread, I just can't see them keeping up with a
percentage increase like that.