Suggest free (rather) low-spec games

Pretty much any genre is alright, but I am NOT interested in turn-based strategy games. I'd also like that the game would have at least some kind of player-base, so that I won't be playing the game literally with 24 other people there. Why I am asking for low-spec games is that when I am at my father's place I can't play games such as ArmA 3, Battlefield 4, CSGO, GTA V, etc. etc.

Specs:

AMD Phenom 9550 @ 2.2 GHz

ATI Radeon HD 3600 Series (not integrated)

4GB Ram

Windows 7 Home 64-bit

4GB Ram (4x 1GB sticks)

450 GT HDD

Pong

The Suffering

Brutal Doom : Hell on Earth starter pack

Warframe

Blacklight Retribution

Quake Live

Star Wars : The Old Republic

Team Fortress 2

Alien Swarm

Infact you can find quite alot of games if you simply google Freeware games, plenty of games out there that are Free to Play or some gotten so old and titles not claimed by companies that they've been given a freeware status.

If you like mobas, Heroes of the Storm is my current favorite. :)