There are some good ideals on this growing list. I shall try and add some new or slightly tangent:
Completely assemble one of your own design in whatever factory alongside the actual assemblers. As slippy says, curse the day you decided to conceal the fasteners, and you can enjoy your bleeding knuckles when you learn about tool clearance.
Create an image reference library. Inspiration can be hard sometimes.
Patent something.
Write an article for publication, any venue is fine.
Take a continuing education class in something like law, accounting, project managment.
Volunteer help produce a conference, seminar, class.
Be tested by a value: the inevitable classic is to be asked to copy something or design something unsafe.
Go to a graduate show and actually engage the students in interested discussion. Although, probably you should do this more than once.
Have a meaningful talk with a CEO, CFO, about business, not just hiring.
Have a humbling experience somehow related to your work (for me it was a young guy explaining, after I had made what I thought was an innocent comment on advancement, that he would be perfectly happy to work in this factory for the rest of his career.)
Give your mother something you designed regardless how esoteric it is.