Left 4 Dead

Developed by Valve and released on Steam and Xbox 360 in November 2008, it introduced a highly replayable co-op experience powered by the AI Director, which dynamically adjusted enemy placement, pacing, and item spawns to keep every playthrough feeling different.

The best aspect of the gameplay by far, special infected provide unique dangers for the players, all of them encouraging you to stay sharp and play with your team, as well as opening up dangerous combinations with one-another.

The best ones are obviously when they're funny, like all the messages making fun of the love note that a lady wrote, but there's also some nice worldbuilding and interesting dialogue to read over.

Infinite Melee shoves & you can actually see your legs in First-Person unlike Left 4 Dead 2 just to add to that.

Strong atmosphere: The campaigns create tension through sound design, lighting, and fast-paced action rather than relying solely on jump scares.

Even years after its release, it remains the gold standard for cooperative multiplayer shooters.