Engraving ideas on a pocket knife for boyfriend?

My boyfriend is in the military and for his birthday, I plan to get him a knife and have it engraved. I really don't know what to engrave the knife with though. I'm going to put either his initials or last name on it for sure, but I also wanted something that would remind him of me. But considering it is a knife, I don't want anything up "lovey." what do you think? Our relationship is somewhat ling distance, also. Please I need suggestions !!