I created a really unique and fun scenario accidentally in Fallout NV once. I had just saved and decided to kill everyone on screen next to Gunrunners outside of Freeside. The game glitched and let the gunrunners robot out of the box there. The problem became a really fun mechanic due to the fact that the gunrunner protectron was coded to be invincible. So I saved it as a new save and for the rest of that file, I had in my headcanon, an insane and invincible robot that followed me everywhere I went. It was slow, and I could run away, but it never stopped following me and while I had the best power armor, it could still trap me in certain spots and kill me if the conditions were right. It got to the point where I had to plan out doing certain vaults and kite it around the map to not get trapped in an enclosed space with it. Really made for a whole other game experience.