If you've been throwing out punches in Arms and wished the Joycons were a little more practical, here's a set of grips that changes everything.
The knuckleduster-like Joycons are a 3D printed add-on to the Switch controllers, which you can grab for free from Cults 3D. The end weight of the attachments is about 16 grams, and the designer notes that there's a version with support included to ensure that the knuckle grips fit the Joycons smoothly.
If you have access to a 3D printer, and you'd like to make your Switch a little more accommodating, you also might want to check out this grip that allows the Joycons to be held in a similar more akin to a PS4 or Xbox controller:
Not as cool as neon knuckledusters, though.