The Edwards Air Force Base in California (ICAO code KEDW) is another favorite one, having the largest runway of the world, perfect for testing new aircraft — again, just like in the real world.
The Edwards runway is three statute miles long: in a small enough plane, you can take off and then land without going around. The first tutorial in Flight Simulator X is to do just this in a small ultralight, making this as beginner friendly as possible.
Arguably, the airport closest to your real home could count. Especially if you can locate your home from the air among the randomly generated scenery in what is essentially finding a Needle in a Stack of Needles.
Crack Is Cheaper: Some addons for the simulator (planes, scenaries, etc) are as costly (or more) than the game itself, partly because designing a good plane is extremely hard, programming-wise, not to mention having to pay the license for the use of the jet in the simulator. Luckily, there's lots of freeware addons you can use, too.
Misblamed: Somewhat, as the September 11, 2001 terrorists trained with this program for carrying out the attacks, even if they also trained with real planes. This is possibly one of the reasons, along with lower sales and Microsoft shifting from PC games to Xbox consoles, why Microsoft decided to kill the series.
Most Annoying Sound: The GPWS (Ground Proximity Warning System) in modern jetliners, sure it's useful when landing but otherwise it tends to be bothersome.
The variometer in the DG808S lets you know (in level flight at 80 knots) if the air is rising or falling but there's also a loud, electronic beeping that makes it unbearable. You can turn off the variometer itself easily for some peace and quiet but that will turn off the gauge itself, meaning you have to remember to turn it back on when looking for thermals, ridge lift and wave lift.
That One Level: Just like in Real Life, some airports are notorious for being a pain to land on them:note The list excludes airports whose landing conditions relays on artificial means, like the Ronald Reagan Airport in Washington, DC, due to the large amount of no-fly zones the pilots had to avoid and one of the reasons that airport is off-limits for non-American planes.
The Benito Juarez Airport in Mexico City (ICAO code MMMX) is notorious for being a pain to land, both in the game and Real Life, since you have to avoid the mountains surrounding Mexico City. If that wasn't enough, if you're using real weather it's hot and high, meaning that the air is thin enough to complicate take-off and landing.
The Kai Tak airport in Hong Kong (ICAO code VHHH, now used in Real Life by its replacement, the Chep Lap Kok airport, whose ICAO code in FS is VHHX), despise being closed in 1998, still appears in all versions of the game, and both the real one and the video game version of it are the most difficult airports to land over there, since you have fly over Hong Kong City and sometimes over their buildings. No wonder why it was closed.
Trying to land into an aircraft carrier. For an extra challenge, try to land into one with an airliner.
The Sunan Airport in Pyongyang, North Korea (ICAO code ZKPY) is an inversion of this trope: The most annoying part of this airport is taking off, since the runway is too far from the boarding gate and you need a lot of time for taxiing just to be able to take off. On the other hand, landing on this airport is very easy.
Landing at SABA, which has the shortest commercial (asphalt) runway in the world. Though note how one player manages land with a 747 (granted even at full realism settings, the stopping distance of jets, particularly the 747, is much shorter than real life. Regardless that's still a major achievement).