1. Getting laid off from a job you like due to no fault of your own. Really - it's a 21st century rite of passage.
2. Getting stopped for a (minor, very minor) traffic violation and attending traffic school - you'll be much more aware of bending the rules when you have "points" on your DMV record.
3. Vote - it doesn't matter who you vote for as long as you know WHY you are voting for them.
4. Take care of a pet - even if it is just a friend's pet - for at least a week. You'll get to experience the unconditional love of a living thing and won't have to obligate yourself to the long term commitment if it turns out you hate it.
5. Go on a trip to a country where you do not speak the language and don't hang out with the other Americans.
6. Work in a customer service/wait staff /retail job - you'll never be rude to those service industry employees again.
7. Baby-sit kids for a whole weekend - again...they don't have to be YOURS, just see what it "feels like" to have another human being depending on you...
8. Volunteer for an entire day - pick any cause and go with the intent of paying it forward - when it's not all about you it feels great afterward - don't just take my word for it.
9. Assemble furniture from Ikea or any other big box company - it can try the patience of even the most Zen-like person - and teaches you to at least read directions in life when they are available - following them is another subject.
10. Get dumped by someone you are crazy about - ask for pain? Yeah, pretty much. It teaches you a lot about being a better friend, not taking others for granted and that the heart is a very resilient body part.