2. To not be afraid tinkering with PC hardware and Windows. (If it wasn't for games, I'd probably had no reason to tinker much, besides maybe trying out Linux).
3. I've learned quite a few historical details from playing e.g. Age of Empires 1-2, and they sparked me to search for more information about certain historical characters etc.
In the school, I didn't find history a very interesting subject, as in the exams etc. it didn't feel much more besides learning important names and years. Even if I might not be able to tell when and where exactly Alexander the Great was born or died or I don't remember his parents' names, I still found it fascinating to read more about his life and battles, or Genghis Khan, or Attila the Hun, or or or... Man, those psychopaths really got to fulfil themselves in their lives!
4. Circle strafing and rocket jumping. I'm sure they'd be very useful in real life gunfights.