A billion is a LOT of money. 100 mil or even 10 mil would do a lot.
But let's go with a Billion.
I'd give enough to all family members, and close friends, that not only all of their debts/loans/etc were paid off, but that they would have plenty to spare, like each family member/close friend would get a million extra after their debts were paid off. I might have a disclaimer that half of the mil would need to be invested in a good, solid, investment portfolio. I would even be willing to hire a professional to set up such a portfolio for each person, and maybe even just set it up for them so they can't blow that investement money, and put it in a trust or similar so they can't really touch the actual investment $. So they'd all have a great investment portfolio plus a half mil to do whatever they wanted with it.
For myself, obviously house, etc, debt would be paid off (duh). Then I would want to hire the right person to set up a long term investment portfolio for myself. That could be a ten million dollar portfolio, or even 100 million. But it would be there so that no matter what, I would be set up for life making a large sum on the investement yearly.
Still being selfish, I would definitely move from the state I am in (Montana). I am in the process of making that change in 2024 anyway, but having countless millions to spend on multiple houses in great locations would be nice. Somewhere tropical, plus somewhere that is still in the "mountains" but not cold-assed Montana mountains. Like the Flagstaff AZ example posted by another poster ITT - a place like that in a warmer mountain area like AZ offers.
But I would still like to have at least one, if not more, tropical homesteads. Like large palm trees hanging out over white sand private beach in the Carribean for example. Or maybe even an island in such a location.
I would have a quite large Yacht. My parents have always dreamed about having a house boat down in southern FL or similar. I could make that dream come true. So probably over a mil for a yacht. I may even buy a nice plane. Always dreamed of having my own plane, although at this point I think that urge has left me for the most part.
Travel, nice vehicles, etc, would be a given for how I would spend some $. Being able to go to whatever sports or similar event I wanted, would be awesome.
But after all of that, I would like to find worthy, honest charities to give to. No idea what charities, but I definitely would not want to hoard such a lare sum of money and not give at least half of it away.