The Il-2 Sturmovik. Total hell in the hands of a good pilot.
I took the position of base defense with it once, and the wonders it did... A Bf 109G-2 and a Spitfire Mk.V got on my tail, so I took to the rear gun. I unloaded about 60 bullets into the 109's nose, and I got its radiator and oil. He turned, lost energy, and hit a tree. I then opened fire on the Spitfire, hitting the cockpit and fuselage several times. The bastard killed my rear gunner, but I had the last laugh --- I was still alive, and the Spitfire exploded. My job complete, I landed.
Oh, and *never* underestimate the Il-2 as a dogfighter. It will be your undoing... They can out-turn almost any plane. I shot down an F6F-5 and a Seafire II this way.