I'm all the time adding to my little list. I don't have big aspirations or anything, just some things I'd eventually like to try. I'm no big horse rider, just mostly a trail rider for fun.
Here are some of mine in no particular order:
Learn to drive a cart/teach my horse to drive
Horse camping (I know not a really big deal, but something I've never done)
Compete in some type of horse show or speed event
Ride my own horse on a beach--not sure how I will accomplish that since I live 2 states away from the closest ocean!
Multi-day packing trip
Try mounted shooting
Carry a flag for a parade, rodeo, etc.
Cattle drive, calf branding/vaccinating, roundup or something like that
Be a part of a historical reenactment/show/rendezvous/etc.
So share yours!