The main reason im starting this is that, there is a lot of amazing free games out there, either theyre indy games, or games from the past that went free. Personally one of my favorite free games is Tyrian, its a vertical shooter that is unlike most vertical shooters. Its actually fun to play and keep playing even if it gets relentless.
Here you go if you want to try it :3 http://www.gog.com/game/tyrian_2000
I guess you have Steam, if not, get it. There's a lot of free games available for download there. Team Fortress 2 is one of my favorites. You could also visit http://armorgames.com/ or http://www.kongregate.com/. There's a lot of free games there too.
For a long time I've really enjoyed Blacklight: Retribution, even though it's nowhere near as active as it used to be and isn't very good anymore
One I do love though is the Black Mesa mod; not sure if that counts though
+1 to TF2, it's great!
Interesting game, nice ending.
http://www.freeindiegam.es/2013/10/timeframe-tyler-owen-clark-aboud-alex-senechal/
I think Black Mesa count because it is basically a remake of HL1
Tf2 +1
Path of Exile and War Thunder
warframe
Path Of Exile, Tribes Ascend, TF2 - My top 3 favorites