I used to run YSFlight on my work PC, it's a basic flight sim - not in the league of FlightGear, but still good fun, and quite a lot of add-on stuff for it, and an easy(-ish) map creator. Best of all it doesn't need a great deal of CPU or GPU power - hence had it at work (I sit alone in a large office most of the time...), and better than stock FSX it has weapons!
