Ooh, this is my favourite game!
Absolute first thing i’d do is backflip out of work giving the middle finger to everyone on the way out; while giving my colleagues enough money that they’d leave too and really leave the company in the shit 
I’d buy a naice house, get a housekeeper/cleaner, marry DP, get pregnant immediately.
Would give away millions to family and friends.
Would set up some sort of charity foundation which could do some good in the most productive way, but i’d also have massive fun donating a shit load to the teeny tiny charities as well where my money could go a long way.
Long term, i’d go on lots of lovely holidays and employ a personal trainer to bully me into shape.
I’d buy all the latest gadgets, but I’ll never be the sort of person to spend thousands on a handbag. I think i’d get much more pleasure by giving the money away.