My take on a stick grenade, inspired by the stick grenades used by various armed forces in the conflicts of the 20th Century. Should be scaled for use with 28mm heroic miniatures. I'm printing a test right now to see how it turns out.
For FDM printers, I recommend using full infill and fine resolution, as this is a small item.
I used Blender and created several simple shapes based off my notions of appropriate measurements for the different parts of the grenade. I then combined all the parts and did some clumsy cleanup to get the model to be manifold and print nicely.