1. TeeWorlds
2. Multiplayer 2D Shooter/Platformer with lots of mods
3. It's fast-paced crazyness arcade with gameplay having good part of physics (how you move) and clean graphics. Your tee has a hook and double-jump which are essential for platforming part, and several distinct types of weapons. Yet not sure how it works? Check this 2on2 CTF video and see how hectic it can be. And remember, LOTS OF mods.
4. C'mon, how many platformers do you know which are MMO? Now add that it's shooting fun and free! Also, (did I say it already?) there are many mods ranging from races and sports (how about basketball, huh?) to ctf and dm and many more unique, just for everyone's taste. This thing even got Warcraft3 mod where you can be elf or undead or orc, etc.
5. It's available for PC and Mac for free, just check http://teeworlds.com
6. Through godly word of mouth, just as you ;)
