NOTE: Game Boy games were never sealed in Japan, though I know for certain that it was never opened.
I'm selling one of the rarest Game Boy games unopened, which is Nekketsu Beach Volleyball.
Brief description: Nekketsu Beach Volleyball uses a custom sound driver for playing voice samples and music if played using a Super Game Boy. Never sold outside of Japan.
Taking offers. My ideal price is somewhere around $120. Taking offers or trades. Pictures will be available by request.