A craft fair where you charge a flat fee per table.
In my experience, people always pay lots of money to see "humiliating" things. I recently raised £500 by taking a fully-clothed mudbath! It was actually great fun! It's not everyone's cup of tea, but if you're brave enough to be laughed at in the mud, you could try it. It's cheap to set up too.
A yard sale from donated items, a motorcycle ride, a walkathon or a 5k run, a golf tournament .... What kind of charity