Great idea for a 21st birthday! "Life Lessons" everyone at the party writes out a life lesson they've learned over the years and rolls it up like a scroll and puts it in the jar. Give it as a gift at the end of the night. It's a keepsake from their 21st and an inexpensive but meaningful gift.
21st birthday gift- OH SHIT KIT for the hangover the day after! "Oh Shit Kit The day after your birthday you may be hungover....so we put a kit together to help you get sober. Some sprite, some tissues, and even a snack - don’t worry girl, cause we got your back!"