There seems to be a free trial of a major game almost every weekend and Injustice 2 is the latest title to let you play without having to pay a penny.
Starting on December 14th and running through to the 18th the free trial will let you play chapters 1-3 of the game’s story mode, all multiplayer and online modes, and the full roster of the game’s base characters with the odd exception of Brainiac. You will also get try to select DLC characters in the single player Multiverse mode
The free trial will be available on Xbox and PS4 and if you like what you see you can pick up the full game for half price during the trial.
Source: Press release