Kerbal Space Program

Kerbal Space Program is a game about a green humanoid species, named Kerbals, starting a space program. Superficially similar to Orbiter, the difference between the two has been likened to the difference between making to-scale miniatures for architectural design and playing with LEGOs with rocket fuel in them. In its current state the game is little more than a sandbox. You're set loose upon a space center complete with a vehicle assembly building and a launch pad, a bin full of rocket parts, ground personnel composed entirely of yes-men who build and wheel onto the launch pad anything you design no matter how crazy it is, and some astronauts to crew your creations.

Its official website and download location is here, and a trailer for the game can be found here.

This game contains examples of the following:

Artistic License Engineering: Many of the most tedious and frustrating elements of aerospace engineering (e.g. wiring, life support, random part failure) are simplified, abstracted or eliminated. The remaining challenges of propulsion and control are hard enough on their own.
Art Evolution: Examining screenshots and videos from even a year apart shows remarkable development of the game.
Ascended Meme: One of the loading-screen messages is "Adding K to Every Word", an activity that used to be very (some would say overly) popular among fans. It's less of a thing now, but odds are still very good that an addon's name will have hard "c"'s replaced with "k"'s.
Cloudcuckoolander: Jebediah Kerman, who always smiles all the time, no matter what is happening. Unless something goes wrong.
Colbert Bump: Sips of the Yogscast posted a video about KSP. Minutes later, the server hosting KSP's website and forums imploded.
Fantasy Counterpart Planets: Each planet in the solar system is based on one or more planets in [The Solar System|our own]].
- Moho is based on Mercury (small, closest to the Sun)
- Eve is based on Venus (roughly Kerbin-sized -- actually somewhat bigger than Kerbin, unlike Venus -- with a thick atmosphere).
- Kerbin is based on Earth (third planet, life-bearing, with very varied biomes, and a big Moon)
- Duna is based on Mars (red, smaller than Kerbin, with a wispy atmosphere and ice caps)
- Dres is based on Ceres (quite small)
- Jool is based on Jupiter (large gas giant, with lots of very varied moons)
  - Laythe, Jool's innermost moon, may be inspired by Titan, one of the Moons of Saturn, with its atmosphere and oceans.
  - The orbits of Laythe, Vall, and Tylo are in a resonance just like Jupiter's innermost three moons Io, Europa, and Ganymede
- Eeloo is based on Pluto (smallest and most distant).
Game Mods: Lots of them! Part of what makes KSP so popular is that players can mod almost any aspect of the game to their hearts' content.
Little Green Men: The Kerbals are these, to make it more acceptable (and funny) to lose them in accidents. Version 1.0 will be bringing Little Green Women to the program as well.
Oh Crap: Bill & Bob Kerman always look worried whenever the spacecraft is doing anything other than holding still. All characters do this if something explodes. If Jebediah ever stops grinning... see above.
- Bob will always look terrified. He'll only calm down if the craft is confirmably drifting back to the surface slowly via parachute or has come to a complete, safe stop.
Obvious Beta: Initially very much so, as the game was released while quite early in its development (2011, with version 1.0 due in 2015).
Sci-Fi Writers Have No Sense of Scale: The developers avert this but the use of this trope in media has caused some confusion among players less familiar with actual astronomical scales. Even among those familiar with space fight don't always remember exactly how big space really is. For instance, some have suggested ignoring time acceleration (ie being able to increase the speed of the game) and instead allow the program to run essentially in the background to allow for realistic flight during extended missions. Even acknowledging that a single mission would very well be months long, they don't seem to realize that most of that time would be spent doing... nothing.
- The distances are less than they would actually be, but that's due to the Space Compression. The scales for Kerbin/Mun/Sun are roughly the same as for Earth/Moon/Sun accounting for it.
Self-Imposed Challenge: Making ridiculous rockets, making manned ballistic missiles, making space shuttle equivalents, spacecraft that look like specific patterns, achieving orbit, reaching relativistic speeds, getting a huge and completely pointless concrete cube into orbit, landing on the Sun, landing on the moon, landing on the other tiny moon, etc.
- As the game has grown in scope, so has the scope of the challenges. For example, the so-called "Jool-5" challenge, to send a single vehicle from Kerbin (often assembled in orbit, but sometimes launched in one piece by an even bigger rocket) that can visit and drop a lander on all five of Jool's moons and come back to Kerbin.
Snowy Screen of Death: It used to be that the individual video feeds for each Kerbal would cut to static when they were killed. No longer the case now that Kerbals can exit spacecraft for reasons other than death.
Space Compression: To cut down orbit times and prevent the game from becoming astronomically boring, the planet is a mere 1200km in diameter (1/10th the size of Earth). This also reduces the required sizes of rockets, making rocket design less demanding on players than it is for real-world space agencies. To put it in perspective, a rocket that can get into orbit around Earth could fly all the way to the surface of Duna and back.
Space Is Noisy: Even in the depths of space, you can still hear rockets and explosions.
- Partially justified in that most of those explosions happen either in-atmosphere or when you're still attached to the thing blowing up/making noise, giving the sound a medium on which to propagate to your ears.
Stuff Blowing Up: Rocket fuel is an explosive after all.
Video Game Caring Potential: Some players equip their crew capsules with parachutes and try to land them as close to the Kerbal Space Center as possible...
Video Game Cruelty Potential: ...while others take gleeful pleasure in sending the hapless trio to die in the cold blackness of outer space. Or just blowing them up.
Wide Open Sandbox: The appropriately-named "Sandbox" game mode. Once a Science or Career mode save has enough research, funds, and reputation, they become this as well.