RIPMAX Flight Simulator
I managed to get a copy, but it wasn't easy. I had to track it down and order it from a shop in the UK.
I don't think it's ever been officially released in the US and support elsewhere seems to be minimal. None of the add-on fields or planes have ever materialized. They update their website about every 6 months, from what I can tell.
As far as flight sims go, it's more gamelike than some. Not too many RC sim aircraft come equipped with machine guns. If you're looking for realism, stick with RealFlight.