Hmmm, I think this is what I'd do:
First I'd give a little to my parents so they could pay off the mortgage.
Theeeen, well I think I would invest a bit in something reliable, then put some more in a high interest account.
I would probably also buy some land (I'm only 16, but my parents and me have been dreaming of having a quaint cottage somewhere with a few dozen acres)... though maybe not because there are taxes and other things to think about, but I'd definitely put money away so I could buy land later and have a small rescue.
I would keep a few years supply of riding lesson money, and indulge myself with more riding lessons, and go to this really awesome (but expensive) summer riding camp in NY where you ride 5 hours a day (sigh, heaven)
. I really want to go there because you work with professionals and they teach you a bunch of stuff about everything!
OOOOH AND I'D GO TO THE KENTUCKY DERBY!!!!!!!
And I'd help my parents pay a really awesome vaca this summer because my mom is in great need of a good one. She deserves a major one big time.