Activision is opening the full multiplayer for Call of Duty: Infinite Warfare this weekend. There are no level caps in place and all progress will carry over to a full purchase of the game. The free weekend is through Steam and runs until 1pm PST on Sunday, February 26th. In addition to the free weekend, the game itself is 50% on steam. Seeing as the longevity of most FPS games is in the multiplayer, it's a great chance to try before you buy.
More details can be found on Activision's blog. You'll note there that this free multiplayer weekend does not include the main story or co-op (so no Zombies).