http://www.businessweek.com/magazine/content/06_32/b3996068.htm

The Business Week reports that the army has learned what every third grader already knew!  If you mix certain things together (Think water and corn starch) they mold like mud, and when you hit them with force they react like a rock.  Let me dig out my kindergarden diploma so I can reproduce a few, just with different names 🙂