While it's not an especially amazing game, ClayFighter: Sculptor's Cut is one of the most desirable titles in the Nintendo 64 library purely due to its scarcity.
An updated version of ClayFighter 63⅓, it didn't get a general retail release and was instead sold as a Blockbuster Video rental exclusive. This has resulted in copies selling for insane amounts of money on the secondary market – and it's not uncommon to see associated items going for silly cash. A decade ago, even the manual for this game was worth $1000, but you ain't seen nothing yet.
A till receipt for the game is currently selling on eBay, and has been bid up to the value of $510 Canadian dollars (that's about $370 USD / £303). To recap, that's over five hundred Canadian bucks for a piece of paper – not even the game itself.
If it's the boxed game you're after, then you might have to consider remortgaging the house, as a copy sold in August for almost $5,000.