Whatever you do.... no knick knacks. Especially since APO is for guys too. Most guys are not into knick knacks. Which you probably know though being a guy yourself.
Although I love the sorority "stuff" I have received from various conventions/ events, and I do display it around my house, at this point in my life I'm trying to declutter said house. I have no where to decently "get rid of" sorority stuff, until a new chapter is started!
I love the grocery sack idea, or any tote. Also like the to-go mug.
I have seen customized/ printed flash drives before. That would be very useful, and small so as not to take up a lot of room in the suitcase!
More knick knacky is a Christmas ornament, though not everyone celebrates Christmas.
Good luck with the decision.
Always fun to plan stuff.