D&D 5E: Expedition to the Barrier Peaks (Original Adventures Reincarnated #3)
Originally run was a tournament adventure at Origins II, the adventure was published by TSR in 1980. Expedition to the Barrier Peaks is a famous adventure module, because it mixes “science fiction” and “fantasy.” For this reason it is both well known, and an enduring favorite for those who played it during its heyday. The 5E conversion is consistent with the original design principles, and also offers new avenues for exploration.
In the adventure, characters come across a spaceship that has crash landed into your fantasy world, and have to deal with the consequences. Which include robots, plant people, and a zoo of alien creatures. And ray guns. It has ray guns.