Tactical Fan Boy posted this up. Firequest has a 12 Ga round that is loaded with powder and confetti.

This ammo is for theatrics and serious amusement! The shell is packed with powder and colored confetti. When shot, it will make a large circle in the air between 10 and 15 feet in diameter. The paper then blows away in the wind. Great for parties and plain old fashioned fun! This is a spectacular round and must be seen to believe. 2&3/4″ round.

They come in packs of 3 or a box of 25. You can find them on their website.

This is the only video I could find, seems underwhelming.