I thought reading in the bathtub was a good fit until I got to #7.
Word games are free, and you can play them with friends, though I can’t think of any you can play alone (unless you’re playing against a computer/website.)
There certainly are word games you can play alone, if you count things like crossword puzzles.
Video games.
“Not a complete waste of time” wasn’t one of your criteria.
You may consider it wasted time but when the zombie apocalypse comes I have been highly trained to fire a virtual assault rifle. Lets see all the knitters and stamp collectors say that.
I can’t find a single flaw in this logic.
Juggling. Get three lacrosse balls, it should keep you busy for months.
Get five and most people are set for life.