The best development in home flightsims since they first became available many years ago is the virtual reality head mounted display (HMD). I've just got an Oculus Rift, and basically it is as though you are in the cockpit, you can look anywhere, even behind you. You can even move your head around to look around the cockpit framing.
My favourite sim to use it with at the moment is DCS where you can fly a Huey as mentioned above, but also a P51 Mustang and an extremely detailed A-10. When I say detailed, it takes about 10 minutes from a cold dark cockpit just to set all the switches and get the engines started.
Apparently it works with FSX as well but haven't had a chance to try it yet.
One of the striking things is how much more realistic it makes flying in the circuit, where you can glance across to the runway threshold and gauge your position.