My favorite writing prompts are from dreams. I have "home brewed" story ideas if I write them down fast enough in the morning and can read my chicken scratch when I sit down to write for the day. These are original prompts, thanks to my subconscious. I collect my dreams in a journal.
I also keep a document of interesting articles, characters, and one liners that might inspire a story later. Then I can take two or three and combine them to create a prompt in the moment.
But sometimes, I sit down to write and want a mini break from my current project. A writing prompt would be an excellent choice rather than staring at the blinking cursor and letting my fountain pen drip ink on the page for two hours.
So writing prompts may stir the writing juices and start flowing words.
What are your favorite prompts? Happy Writing!