Hmm. Off the bat:
1) Selfish stuff. Buy a flat in Glasgow. Buy a flat in Berlin. Buy a flat in New York. Buy a flat in London. Buy an iMac. Buy a nice pair of shoes. Buy a shedload of books. A yearly train ticket for the whole of the UK (if it exists). That sounds really sad, but I love the idea of being able to jump on any train any time I like to go anywhere.
2) Slightly less selfish stuff. Buy my parents a nice house and a nice wedge to retire on. Make sure people I love are sorted.
3) Set up a design studio that does work for a nominal fee or free for people that deserve it (I/we decide who this is!). Charities, environmental causes, new businesses, small companies, books that need to be published but aren't, etc. It wouldn't be saving the world in the conventional way, but good design goes a long way to making things that aren't otherwise seen as worthy/trendy successful. And something not being financially viable wouldn't be a problem, whereas for a profit making company it would.
Unless you meant what would I do if I had joined Disney? In which case I'd have told Disney where they could get off, hefty shares or not. Even as a kid I thought they were tacky as hell. The Flumps were where it was at. 😀