Basically just the CPU fan, case, and PSU (if you're lucky). If someone can figure out how to get Doom running on just those 3 things, young people will be able to ascend.
All but the cheapest fans these days are buyitforlife material. The only thing really gonna fuck up a modern fan is epic amounts of dust binding up the ball bearings. And many fans these days use a newer magnetic type system where there isn't even any physical contact being made to wear anything down.