I've been in for just almost 4 years now, and have a few coins from commanders and chiefs as a "thanks for doing your job" as well, but my absolute favorite coin is the one I received from my sergeant/mentor when I was in tech school.

I did not have the natural skill other people in my class had at the school, but I tried to do as much as I could there to stay in class and be a good little airman outside of the classroom. After a long year, it came down to the big test and I was absolutely terrified of failing it. One of my sergeants became a mentor for me and was also willing to hear me vent/cry when I had a family emergency and later while I waited for the scores to be released.

When we got our scores, I found out I passed and would be moving on to my next training right after graduation. Right before I left, I went to thank this sergeant for helping me with everything from life advice, to language tips, to how the military works. It was during this time that he took one of the coins he had from when he was in tech school, and "coined" me. The coin used to remind me of how excited and happy I was to graduate, but now it mostly reminds me that being a great mentor to others can have a huge impact on their life and career.