The beetle has been in the series since Smash 4, and is a pretty good weapon in the series. Its game of origin is The Legend of Zelda: Skyward Sword where it replaced the boomerang as a pretty neat far-range weapon.
In the Smash series it’s a throwing item. It also looks a lot like a piece to the giant laser weapon, so I often think I have a beetle when I do not.
But it’s pretty easy to miss with the beetle. So make sure your aim is true.
And if you do your opponent is carried away to their doom. It can also be countered/reflected which I have done to other people. Which I found hilarious.