The first is one which you can throw around, the second is a small scale one and the third is a coaster, a 3D minimalist art piece for your wall, mousepad (if it is made to a larger scale), or a cool custom gift card for that explosives enthusiast in your life.
To make the throwable one you need:
Some 15mm thick foam/foamrubber
Scissors or other cutting implement
For the tiny one you need:
A ball bearing
Some thin wire about 0.8mm thick
Some pieces cut from a soft drink can
For the flat one, you will require:
Some 2mm thick foam rubber (or another flat material you think will work)
Step 1: Throwable Grenade
This is the most simple grenade in this instructable, with only 2 parts.
The first part is the squash ball. (You could use a bigger ball if you have one, but the rest will also have to be scaled up then.)
You don't need to modify the ball at all.
The second part is the combination of fuze, primer, and arming trigger. I have included an MS paint template for you to print, cut out, and trace onto your foam. I have labeled 3 parts, (1) is the main piece to be cut out. (2) is the ball, only for size reference and scale. (3) is a part of part (1) only labeled as a part because it isn't rectangular but cylindrical. To round the corners and achieve this cylinder shape I used a knife, but I suppose you could melt it to shape with a soldering iron to save time.
Once the foam part is done, glue it on the "top" of the squash ball. It is complete!
It is great fun to shout "GRENADE, CATCH!" and toss it towards a particularly gullible friend or colleague to see them jump.
Step 2: Mini Grenade
The main part of it is the ball bearing, which you can find in a lot of places. I didn't take any pictures during its construction (sorry) but it doesn't really need any because it is so simple. Apart from the ball bearing it needs 4 pieces; a pin (bend wire into a small coil and clip a circle off), the fuze (wrap a strip of can metal into a cylinder) A primer (bend another small strip of can metal into a sort of top and bottom -less cube which fits snugly around the cylinder) and the trigger(bend another piece of can to a sort of elongated isosceles triangle and then bend most of it down, leaving a square to cover the top of the primer, and bend the bent-down piece about halfway down to an angle so it looks like a real one)
Once you have made these component parts, you'll have to put everything together. Glue the primer around the top of the fuze cylinder and then put some wood or foam into the cylinder so that it can be glued to the ball bearing.
Glue the circular "pin" to the one side of the primer. Then glue the trigger (square bit) onto the top of the primer. Glue this whole thing onto the top of the bearing. I ground the bottom flat so that it can stand upright, but this is optional.
Step 3: Flat Grenade
I used 6 parts to make it (sorry, I didn't photograph the components) and they are all shown on the template.
The first step is to cut part (1) out of your material. Then part (2), which must be glued into the space shown by the dotted lines. The part (2) in the pictures differs from the one in the template because I made an improvement to the design when making the template. Then part (3) must be cut out and glued on the "top-left" part of the grenade. Cut part (4) out and poke a hole in the muddle to fit scissors into to cut the inner circle out and form a ring.
Parts (5) and (6) must be glued with one part of the ring between them, so a sort of sandwich. Part (5) must be glued onto the area shown, then part (6) must be folded and glued down on both sides to cover the one section of the ring and part (5).
Your Mousepad/Coaster/Gift Card/Artpiece Grenade is now complete!