Artifacts in Might & Magic VII.

Well, take, for example, the empty houses in some locations. Or here's another example: in several locations, if you go to the very edge, the minimap will show some buildings that are impossible to reach. Or the lost manticores that can only be found in the arena.

Even in Might and Magic VI, by digging through the program code, I found items that don't exist in the game. I think there are many more of them in part 7.