You know what game series no one ever talks about? ClayFighter. I remember years ago competing in a Blockbuster challenge for it (Blob for life!), and how much of a big deal the Nintendo 64 game was, but alas, it's kind of a distant memory for many.
But it seems as if the franchise is back in the headlines, as the instruction manual for the rare ClayFighter Sculptor's Cut is going for a whopping $1023 at the time of this writing. The reason this item is so rare is because the game itself is not only a Blockbuster rental exclusive, but the inclusion of the manual was optional.
I don't know how many hundreds of pre-jewel case era games I've thrown away boxes for, and after becoming a collector, I highly regret it. If you have any original boxes, keep them!