For a couple years now, I've been a pledger for the upcoming Cloud Imperium Games space-based MMORPG called "Star Citizen." I know the game has its detractors out there, but the plain fact is that for a mere $45 (US) pledge, you can get access to everything as it is released.
Fair notice: The game is currently in very early pre-alpha at this point.
Playable 'modules' currently include the Hangar, a small social module, and an actual game-game called 'Arena Commander,' which includes both combat and racing scenarios.
Upcoming features will include a FPS module called Star Marine, multi-player ship operations, a huge solo-player story game called Squadron 42 (it's like Wing Commander or Freelancer, only much, much bigger), and what will eventually be a huge persistent universe.
In time, that rather low-cost minimum pledge will probably go up in price. There are also other, more expensive pledge packages, plus standalone ships one can pledge for. Some are available to fly right now in Arena Commander, others will only be available later on.
Anyway, I'm putting up this post here so that anybody who stumbles across it and happens to be interested in Star Citizen, if you use my referral number, you can get an extra 5000 UEE credits in game just by using the number when you sign up and buy a pledge package. No strings attached. The credits can be used in-game for weapons, ship components, or decorations for your hangar.
Here's the referral code: STAR-4T5H-RHXK