Fund loads of skate-parks/youth centres/climbing centres in the city.
Fund a bunch of housing projects for low-income families.
Set up a couple of charities.
Start a film production company.
Start a record label.
Randomly fund loads of interesting looking Kickstarters and whatnot.
Buy houses for friends/family.
Lots of travelling.
Once megalomania sets in due to my immense wealth, might try my hand at getting involved in influencing the outcomes of foreign elections.
Cheers