Morrowind because I'm one of those people. But for real, that game in part defined large parts of my life. I got frustrated with the limits of the game so I started making mods, then got frustrated with the limits of the engine so I learned how to make my own. Now I work adjacent to the game industry with plans to get back into the industry proper in a couple years. Making games is all I've ever wanted to do and I owe a big part of that to Morrowind and the construction kit.