Make Games Before Your Tea Goes Cold
Downpour is hands down the easiest game engine you've never heard about. I've always liked the intersection of physical and digital games, and Downpour allows you to explore that in minutes. I used it for my Blossom VN Jam entry, I Have a Poem for You, which was done in one evening when I was down with a fever.
At its heart, Downpour lets you take photos from your phone, make collages out of them, write stories, and link pages together. This means you could make your favorite stuffed animal star in a faux-philosophical musings against the backdrop you doodle freehand on a random receipt. Make buttons out of...real buttons! Crochet your main character!
Or you can just go outside right now, point your camera at the first interesting thing, and let loose. It's a delight to use and something that embodies my casual creation philosophy, something playful and spontaneous and lighthearted.
Downpour comes in a quasi-social-media site accessible mostly from your phone, but it also lets you export the result so you can host it anywhere, even your personal website! This is very important for me and I'm happy to see that it's important for the app creator too (Downpour is run by one person, V Buckenham).