Another cool error that I didn't know existed before 5 minutes ago... http://www.coinfacts.com/error_coins/mules/1999_cent_dime_mule.htm
Sold at Heritage in 2006 for $138k. From Heritage Auction: "Interestingly, the consignor of this piece also owns two of those coins, a 1993-D cent/dime on a cent planchet and a 1995 cent/dime on a dime planchet." Does make one go Hmmmmm.. Don't it?