There are a lot of free games in 2015… here is a short list…
Happy New Year from G4G.it!

Click on the game title link for more info.

WarHammer 40k: Eternal Crusade (to be released somewhere in 2015)
This is not a free game, speaking of, buy it and help making an mmo in the wh40k universe. But you can play as a Space Ork for free.

World of WarShips (will be released in 2015?)
Naval combat, WW2 in full 3d.

Survarium (Open Beta January 2015)
A Stalker multiplayer online type of game, in development.

H1Z1 ( Early Access on Steam start 15th January 2015)
Sony Online’s zombie survival MMO.

Fractured ( Q1 2015?)
A free to play team-based (5 vs 5) space combat game that puts you at the helm of a colossal capital ship.

Armored Warfare
Tanks vs Tanks in the modern era. Until January 18th, 2015, get a free Commander if you signs up or have signed up for the Armored Warfare beta

Battlecry (31st January 2015?)
BATTLECRY is a 32-player online team action game.

Black Desert (sometime in 2015)
Black Deserts is a large scale sandbox MMORPG with spectacular action and battle.

Dirty Bomb (after January 2015)
Dirty Bomb is a multiplayer free-to-play shooter from Splash Damage.

Dreadnought (Currently in beta, Summer 2015?)
A sci-fi, multi-player space combat simulator.

I probably forgot some good games, but there are really a lot of releases next year.