I've worked on a variety of homebrew machines that have unique or interesting (to me) features, and usually something fairly complex on the software side.
Game like the Multi-Bingo https://pinside.com/pinball/forum/topic/multi-bingo-machine and Multi-Races https://pinside.com/pinball/forum/topic/multi-races-the-multi-one-ball-horserace-game were games that allowed for hundreds of machines to be playable in a single cabinet with swappable playfields and multiple unique mechanisms. The Multi-Bingo has been making the rounds since 2016, and Multi-Races since 2019. Very ambitious on the hardware/reverse-engineering side as I tried to replicate the pseudo-random mechanical movement as accurately as possible.
Robo-Frenzy (still in progress) is a scratch build EM arcade game. Wildly complex! https://pinside.com/pinball/forum/topic/new-em-arcade-game
And one of my more ambitious software games was a remake of the original Quest For Glory/Hero's Quest computer game as a pinball. https://pinside.com/pinball/forum/topic/p3-game-so-you-want-to-be-a-hero-quest-for-glory-pinball
This last was only possible because of the P3's unique and groundbreaking features (profile support, an open SDK, and interplay of the ball across a huge screen filled with dynamic targets).
As I wrap up my work on my first P3 game, I've decided to announce a second P3 game! It's called "Ranger In The Ruins" and will be more of a traditional pinball game with an Internet-based twist.
Your goal is to survive for as long as possible/achieve the highest score possible.
Acquiring an item will provide you some kind of assistance (usually).
Also, in a first, when you lose a game, if your P3 is connected to the Internet, some 'ghost' data will be written, which can then allow you to appear within another's game.
It will use the CCR playfield module.
The game is still in early/active development, but I've set up a website: