Created by Reddit contributor dapperrogue, this homemade keyboard is modeled after the Mk 2 hand grenades used by the U.S. in World War II. It has 25 keys in total — six columns of four plus a secret one underneath the safety lever on top. To use that key, you have to pull the pin and then press the safety lever.
Since there aren’t enough keys to cover each letter of the alphabet, dapperrogue instead programmed each key to type out a phrase that one might associate with a grenade, such as “Boom!” or “Kaboom!” The device itself is made from a 3D-printed frame, and all the specs you need to try and build your own are available on GitHub.