For my 50th, I rode in a helicopter over a live lava field. It was fabulous! I recommend it.
There’s always “wine, women, and song.”
Take a trip.
Hire a band for a night.
Have a banquet for the homeless in your city/town.
Go skydiving.
Stay home and drink tea.
Visit North Korea, and do something illegal like breathe, and wait to see what happens.
Pay for a fireworks display.