Best Multiplayer game at the moment ?

Battle-Bit. At the moment it is on development and servers are down until april. (For what I've known)
CS:GO sometimes. I just need to learn some strats for more upcoming challenges.
Garry's Mod. I just can't stop my addiction with this game. I really like the prop hunt gamemode and im still looking forward to beatrun.

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Now that comes to personal preference. The games I listed aren't for everyone.