Verdun

Verdun is a squad-based multiplayer first-person shooter set during the First World War. It was released on 28 April 2015 on Steam, after more than a year in Steam Early Access.

Verdun is inspired by the infamous 1916 Battle of Verdun in France from which it takes its name. The game includes historically accurate WW1 weapons, authentic uniforms and equipment, detailed injury and gore modeling, and maps based on the real battlefields of the Western Front. In addition to realism and authenticity however, it's also rapidly becoming infamous for its difficulty.

The game runs on the Unity engine and was created by independent studios M2H and Blackmill Games. It is also still a work in progress, with the developers continuing to release updates. A free expansion, Horrors of War, was released in March 2016.

Tropes used in Verdun include:

Bayonet Ya: Bolt-action rifles can be attached with bayonets, allowing them to double as impromptu spears in melee.
Cool Guns: It helps that a good portion of the standard-issue firearms on both sides were commonplace, with some even having staying power well into the present. Be it the M1911 pistol for the Americans or the Lee-Enfield for the British.
Doing It for the Art: A major reason behind the game's existence.
Deadly Gas: Poison gas is very much a danger, making the use of gas masks a necessity if you don't want to suffer a painful death. Said gas also conveniently serves as a smokescreen.
Death From Above: Artillery strikes can be called upon by non-commissioned officers on both sides. Though said strikes can be indiscriminate if you or your allies aren't out of the way in time.
Highly-Conspicuous Uniform: French soldiers tend to have uniforms that are glaringly blue. Which is Truth in Television, given how this more or less happened during the actual Great War.
Hollywood History: Averted. The game goes through quite a few lengths to show that there's a lot more to the Western Front than just static trenches. And proceeds to show said lengths in all their harrowing glory.
Imperial Germany: One of the playable factions in the game.
Invisible Wall: Similarly to the Battlefield series, going out of bounds is treated as a sign of desertion and eventually, insta-death.
The Many Deaths of You: There are a lot of ways to die in the game that aren't just from gunshots, be it death by bayonet, gas attack or barbed wire. Horrors of War adds even more ways, complete with your dying soldier pitifully groaning in the ground.
More Dakka: As standard-issue firearms of the period tend to be bolt-action rifles, having a machine gun by default is this.
Nintendo Hard: This is a game where it's horrifically easy to die.
Obvious Beta: Verdun has undergone several updates over time, but continues to be in development even after being released. This is in part explained by the dev team comprised of only four people.
Paranoia Fuel: Enemies, traps and lethal dangers abound at every corner, be it in the trenches or simply by going "over the top."
Real Is Brown: Downplayed, though the overall color palette is fittingly muted.
Scenery Gorn: The Western Front is as desolate and brutal as it is a sight to behold.
Selective Historical Armory: Averted. All the weapons available in-game are what would have commonly been available to soldiers during the Great War, such as the Lee-Enfield, Mauser or M1911.
Shown Their Work: The developers have done their research, which shows in-game. Whether it's the bolt-action rifles used, the kinds of trenches deployed or even the particular gear soldiers would have had on them at the time. The maps themselves are based on actual battlefields in the Western Front.
The Squad: Gameplay revolves around this; simply going lone wolf on enemies is a guaranteed way to die quickly.
Yanks With Tanks: The US military also shows up, albeit as "Doughboys" befitting the era.
War Is Hell: In spades, given how Verdun is set in the trench warfare-laden Western Front, not to mention being inspired by one of the bloodiest battles in the Great War. The Horrors of War expansion also takes this even further, by adding gore and more graphic deaths.
Widget Series: Unlike World War II-themed works, there aren't many first-person shooters, let alone games in general that focus on the Great War.
World War I: The game covers the conflict in the Western Front from 1914-18.