What should I get engraved on a dog tag for my boyfriend?

My boyfriend is getting a short leave(he is in the army) and is coming to see me.He said hes gonna give me his dog tags so he can always be close to me when he leaves again. So for our anniversary/ valentines I want to get him a personalized dog tag, i just don't know what to put on it. I don't want to put his name on it, and I don't want it to be super long.