Well, I use a 30 cal ammo can for a charcoal grill. Works pretty well, to. I can make dinner diner for one on it with 10 briquettes.

If you stripped out the gasket, you might be able to make one into an oven if you stuck it in a hot fire, or layed it on stove or grill. If you went with a 5.56mm can, pulled out the gasket, you might (emphasis on the might) even be able to get it into a "fat-50" can. put a layer of coals in the bottom, then insert the small ammo can, stuff the space between them with more coals, and you have dutch oven.