Super fun party game Quiplash by Jackbox games is currently free on Steam!
Quiplash is for 3-8 players and the game will provide you with a prompt that you answer using your phone. Your answer will be put on screen and the audience will vote on who comes up with the best reply.
Even though this one is free, you can still pick up some free steam gift cards to help pay for other future purchases.
Sign up for all 3 sites to get regular freebies in the mail.