What's something to do over summer that's unforgettable?

what's something do to over summer that you'll never forget?

Do something for someone/s less fortunate than you - lifetime memory.

It depends on your age....

If you're 15-19, go Sky diving or Bungee jumping. Get a parent or friend's parent to go along. They have tandem diving/jumping where someone is tied to you. It's plenty safe and a lot of fun.
If you're 19-22, go on an unplanned roadtrip. One year, we drove from Dallas to Wisconsin just to get Wisconsin cheese. We never made it to Wisconsin, but the trip was great!

Do some fun things that you would normally look at and be hesitant.
Do them anyway (so long as they are safe).
Familycoach

Depending on where you live, You ,might try to volunteer your time at a "soup kitchen" in your area. I know it probably wasn't the answer you were looking for but I did that not too long ago and the "high" that I got from helping someone else out that didn't have the ability to pay me back, was incredible. You might be surprised at how it makes you feel. I have never been more happy in life than when I was helping out someone less fortunate than myself. Good luck! John