Peanut Popguns are a trademark item of the Nintendo character Diddy Kong. They are basically popguns that shoot peanuts, and Diddy Kong has used them in various games. He usually has two popguns at once and is very skilled at using them.
In Super Smash Bros. Brawl
In Super Smash Bros. Brawl, Diddy uses his peanut popguns as his regular B move. The longer you hold the B button, the farther the peanut will fly, but if it's held for too long Diddy Kong will be stunned for a short time.