What are the best free games on steam?

tl;dr answer: Path of Exile, Rift, Dota 2, Emily is away, some visual novels that I can't remember right now :P

Sepia Tears, Narcissu 1st & 2nd, The Sad Story of Emmeline Burns, Carpe Diem, One Thousand Lies, Lucid9: Inciting Incident, The Bottom of the Well, Mystic Destinies: Serendipity of Aeons, Everlasting Summer, Seduce Me the Otome, Voices from the Sea, Without Within, ChuSingura46+1 S, and Lost girl`s [diary]
All visual novels :3

Eve is about to go f2p. Join us :)

Don't know if someone said it, but Brawhalla is cool, a ssb alike game

Carpe Diem
Short Visual Novel, but worth a playthrough.

Close Your Eyes, but I'm a huge fan of those RPG Maker horror-themed games like Yume Nikki and Ib.

Necroing because this thread needs updates.

I´ve been playing "BRAIN / OUT" and It´s pretty fun. Think about a pixel art Counter Strike in 2D, has a crate system, you modify your weapons while gaining parts, developers added some popular characters as skins, like the rooster in Hotline Miami or Big Boss from MGS (You won these with certain achievements I think). So yeah, It´s a simple MP game but really fun. http://store.steampowered.com/app/578310/BRAIN__OUT/

Zombie Panic! Source. This one was recommended from a contact on Steam and It´s really fun also:
http://store.steampowered.com/app/17500/Zombie_Panic_Source/

Other ones I´ve played:

Supraball (Weird Sport´s game, not for everyone)
Alien Swarm (A classic)
Fractured Space (Pretty Cool IMO)
Prominence Poker (Felt rigged at the time I played. Idk If they fixed this).
Sven-Co-Op (HL1 MP)
Hawken (PvP Mechs)
No More Room in Hell (Zombie Survival)
The cat and the coup (Weird Indie game)

Heroes & Generals

Cayne is a short but fully polished game by the makers of Stasis. They released it free to support their kickstarter campaign for their next game, but they could have sold it (and I would have been happy with my purchase). Gore horrific sci-fi point & click very well done, a sort of Statis chapter with different characters. Highly recommended by me :)

I don't know if best, but a cool one :
Relic Hunters Zero

Cinderella Phenomenon

The Old Tree

Double Action: Boogaloo. Cool as ice

if you like point and click puzzle-ish escape the room hind of things, PRICE was great :)

TF2

Its clearly this one
http://store.steampowered.com/app/353360/how_do_you_Do_It/

Serena
http://store.steampowered.com/app/272060/
Quite short, but really engaging 'walking simulator' or rather "narrativ'em up", since the whole "walking" happens in two-room cabin. If you hate clicing on every item (and the do it all over again) - don't ever touch it. Personally I loved this little story much more that overhyped, 20$ 'worth' Gone Home..

I already posted, but I'm also gonna throw in Lucid9, a visual novel.

Everlasting Summer
http://store.steampowered.com/app/331470/Everlasting_Summer/
Russian-made anime styled self-aware meta mystery Visual Novel. I finished it only once, but it's probably the first time when I really want to find out more and see other endings to get the whole (or at least more of the) picture.

Epic Battle Fantasy 3
http://store.steampowered.com/app/521200/Epic_Battle_Fantasy_3/

Decent and fun turn based RPG game

Unturned

Edit : wtf, who bumped this thread before me

When You said You like VN, Chusingura46+01, Dies Irae, and Sunrider Academy just pop out if my mind instantly, only the common route that's free tho
If You like (MMO)RPG I can suggest Mobius FF and WAKFU
for TCG try Shadowverse

for paid VN, just visit my profile if You interested