What makes a good B-Day gift?

Jenna's birthday is on the 21st, and we'll be on vacation during it, so what would make a good gift that I can give her. It has to be something that I can hide in my suitcase easy, but something that will not easily be broken. This is a tough problem to have because it is something that I also have to give to her in front of her parents. Maybe I'll just stick to giving her a card, and then take her shopping for something when we get down there. That, I think, would be the safest.