I've made a couple games, though I am still having a hard time finding the soul of the game in the LLM and haven't released them; there's a historical roleplay game (that I plan to release soon), a storytelling game (the player tells stories to the LLM), a wander-a-world-aimlessly-and-chat game, and I never get further than 50% through the way of murder mystery games, though murder mysteries seem like an excellent structure.
I've built some abstract content development tools, generally focused on building larger content somewhat top-down (defining vibes, then details).
I'm working on a general project helper using the GPT-Vision, voice, and regular GPT. You setup the camera above your workspace, work on paper, and chat with the LLM while you do it. I think there's a lot of potential, but the voice stuff is quite hard to deal with... there's just a ton of stuff happening in parallel, and I find it very hard to code something reliable.
The stack I use is all in the browser, generally Next.js, Preact Signals, and my own code to call into GPT, Whisper, etc. I like having everything available for inspection, and I generally keep all the working bits visible somewhere. (This can be overwhelming when other people see it.)
But I haven't gotten over the deployment hump... the cost and complexity is a challenge. I've used Openrouter.ai recently in a project, and I think if I leaned on that more completely I'd find the release process easier.