An iTunes gift certificate. I bet there are some useful apps. Museum, resto, etc.
Also, I have a nylon tote bag that folds into itself. It has a little clip on it and I attach it to my purse or backpack. The minute I need extra room, voila! It's lightweight, just the perfect size, and strong enough I walked home with a gallon of milk no problem. I got it at Wallgreens for $5. Best money I've spent in a long time.