Thanks for all the advice guys. I ended up getting him a prepaid quick check card so he can either buy food from the store or fill his car with gas. Also included a card, and some other small things for the flight bag and he seemed to like all that.

One of the things I got him was a Sic-Sac puke bag, because he has filled me in on the horrors that come with having a student try to throw up out the window, only to have the wind from the open window push it back in/across the cockpit into an innocent instructors unsuspecting face. (No, I wasn't that student! haha) I gave him that gift just for a laugh, but who knows, maybe one day it will get some real world application and then he'll really be thankful!

The fastest way to a CFI's heart is through their stomach's!!!! Amazing how much "free" ground I'd give for lunch/breakfast