This week is finals week for me, so since i'm kind of wrapped up in some stuff, I thought I would once again bring you a prop from one of the great builders in our community, Wraith 5. So sit back, check out the build, and hopefully i'll see you guys next week! Take it away Wraith:

Materials:

Empty deoderant can
Keyring ring
map Pin
Old Plastic-topped Mousemat.

Step #1: Take your deoderant can, and rip off the lid. (making sure the can is empty first)

Step #3 (optional): I wanted my grenade to have a more futuristic feel, so I cut some handgrip 'fins' from an old plastic-topped mousemat , glueing them around the sides, and repainting with extra scratches and things, as if the grenade has been carried around a battlefield for awhile.

Seeing as the materials are pretty easy to find around the house, I built this again for $0. Assuming you were buying everything, the cost would probably amount to under $10.
For a cheaper alternative, you could probably get away with using drinks cans for the basis of the grenade, though it'd be a bit more flimsy.