This weekend's free entertainment comes courtesy of Capcom. It's Ultra Street Fighter IV—the most Street Fighter IV of the four versions of Street Fighter IV. It's as Street Fighter IV as you can get, assuming Capcom doesn't release an Ultra Street Fighter IV: Arcade Edition or Hyper Street Fighter IV: Revengeance, etc.
Whatever it's called, it does still seem to be about punching (and sometimes kicking) an opponent in complex and ostentatious ways. Should that be a thing that appeals, you can play USF4 on Steam for free until Sunday.
In addition, Capcom has a sale on their entire Steam catalogue. That includes a half-price discount on Ultra Street Fighter IV, as well as 66% of DmC and 80% off the flawed but interesting Remember Me. You can find a full round-up of deals through this link (opens in new tab).
Ultra Street Fighter IV should have automagically been placed in your Steam library. You can install it through there, or on the USF4 Steam page (opens in new tab).