I took ideas from a lot of grenades on this site, and kind of modded them together. It uses very common/easy to find pieces, and takes about 5 minutes to make. If you throw it hard enough it has a blast radius of about 5-8 feet.

P.S. I love critical comments because they give me a way to improve and fix my mistakes. so thank you, haters.

Step 1: Materials

Like I said, you don't need any rare pieces for this.
you need:

16 yellow/gray 5 slot connectors
1 orange 2 slot connector
1 Y connector
2 black/white snowflake pieces
1 blue rod
1 gray 1 slot connector
2 rubber bands

Step 2: Grenade Body

For the grenade body, you take 8 yellow connectors and attach them to a snowflake connector like so, then you do the exact same thing again.

Step 3: Firing Pin

Take the orange connector and attach it to the blue rod. Then take the gray connector and attach it to the y thing.
set these aside, because you will use them later.

Step 4: Rubber Bands

Add the rubber bands, as shown in the picture.

Step 5: Putting It All Together

Combine the two halves of the grenade. then, insert the firing pin and attach the Y-connector. to prime it, just remove the y connector, pull out the pin, and chuck it as hard as you can.