Some apartments that I can turn into transitional housing for houseless and/or low income families, along with a staff of full time handymen, social workers, and counselors for facilities and transitional support.
Create a healthcare fund/endowment investment managed by someone competent. It would be used to pay medical collections debts using the interest it draws.
I dunno. A billion dollars goes a long way. Well above and beyond any amount I ever anticipate needing, let alone having. Maybe some Picassos to hang in my modest house.