I visited Catalina Island off the coast of California. I'm 22 now but I still remember how amazing that trip was. my whole family of 6 went and it was the best present they could have given me. there is so much to see and experience. it is a beautiful place with tons of activists from tours to submarine experiences. if you live in California you should go.
I had 3 friends that had birthdays close to mine so since we grew up together we basically had same friends, anyway we just got together and had just one big party. Karaoke (sp??) dunk tanks, laser tag, water balloons were involved at one point, we had friends that were starting a band so had them. There was a place to play basketball, ping pong, air hockey. etc.. Just things like that and it went over amazingly.