From the Super Mario Wiki
The Grape Shooter is a long narrow blowgun made of what appears to be bamboo. Lanky fires his Grape Shooter by blowing out one to launch a large grape at enemies.
The Grape Shooter can be purchased by Lanky Kong from Funky Kong for three coins at Funky's Store in the area Angry Aztec or any area afterwards. With the Grape Shooter Lanky gains the ability to shoot Banana Balloons, hit Grape Switches and snipe enemies from afar.
Further into Donkey Kong 64 special upgrades to the Grape Shooter (as well as other weapons) can be purchased at Funky's Store. Some of these upgrades include a larger ammo capacity, a sniper scope and enemy-seeking ammo.
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