1. Work out and eat healthy, get in the best shape of your life like previous posters said. You will be in a good habit going into dental school, and perhaps that will carry over despite the hard academic load.
2. Become a competitive eater. Go to a buffet once every 3 days and practice stretching your stomach. *note- #1 and #2 are somewhat polar opposites, it may be best to choose just one and go for it.
3. Learn to grow that sticky icky. I hear if you are always high, time passes you by quickly! Something to think about since you are bored out of your mind.
4. If you don't want to grow it, you could always book a stay in amsterdam, and become a resident at one of the local hash bars/coffeeshop
5. Take a job, no matter if it is tied into dentistry or your degree and save money to start paying off the massive debt you will be aquiring over the next 4 years.
6. Don't listen to me and be original? You could start a scrapbook to keep memories of dental school, go meet someone to fall in love with, become educated on computers (building them, Operating systems -linux, vista, mac osx, etc) you could take up snowboarding and live in the mountains for a month. work on your golf game so that if you are playing with any of your professors in dental school or possible business acquaintances you could really stand out as not terrible, or even perhaps mildly good.
7. Get into showing dogs. Personally I would take out a loan and go purchase 4 of the finest french bulldogs I could find( I love them 😍 ) If they are old enough to breed go ahead and allow them to breed, if not, then grow them up with love and allow them to breed. Then sell each pup for $2000. Each litter they have you could afford to pay off some of dental school. Plus, you have 4 of the best dogs ever!!!
You have a lot of really good options there, let me know if you would like some more.