Are you familiar with the tradition of the Military Challenge Coin?
Here is the Wikipedia entry (easy click & read, so I won't recopy it into here).
I'm collecting coins here in Iraq (natch). Some I am purchasing.
AFTH ICU COIN
AFTH ANESTHESIA
4th AIRCRAFT MAINTENANCE UNIT (From Hill AFB) when I participated in "Medics to Maintainers".
Sometimes a coin is gifted to you.
777th EAS (gift from 1st Lt Parker, who wants to be a dietitian and spent a few days in Nutritional Medicine shadowing me)
And then there is a Commanders coin which is presented (in a handshake) when you do something above & beyond. These are the best!
330th Transportation Battalion - I gave a Nutrition briefing "For the Love of Chocolate" and the Colonel must have really enjoyed it. He gave me this coin in a handshake at the end. Nice!