Fight in rain soaked trenches or charge over No Man’s Land to battle in the War to End All Wars. Use authentic weaponry in your fight with the enemy, call in artillery strikes to take out foes en masse, and coordinate with your team to gain the final victory on some of the most infamous battlefields of The Great War. Screaming Steel: 1914-1918, previously known as WW1: Source is a total-conversion project being developed by devoted modders for the FPS game Day of Infamy.
A excellent game in terms of realism, however I'm afraid it fails at being playable due to the lack of regular players.
WWI: Source. One of the games for a era which there isn't much of a demand for in terms of entertainment, although it seems to be a potential market for anyone bold enough to snatch it up, albeit this mod is free it still could be better.
It's main shortcoming is that there is a large lack of players who partake in battles on it of which is a regular basis. Despite this, even when a few players get around, it can be very fun. The main of the game involves charing towards the enemy, the officer providing support in the form of artillery; gas or otherwise. The purpose of the officer isn't really as the name says though, but rather to give support like the machinegunner class. That being said, the system is something like a rock paper scissor system, where the rifleman beat officers, who beat Machinegunners, who beat rifleman. That being said, it is overall a very enjoyable game, just when you can find a lot of players. But don't take my word for it, try it yourself.