Hogs of war is also my pick - did not think anybody else would mention it. Me and my brother played probably for 100s of hours. Never really multiplayer, but the campaign was excellent! Such a fun game.
And the little things the hogs say before firing a gun, or before dying always made me laugh with their accents. Such an endearing game. And yet quite hard towards the end. Or at least it felt that way in the 90s, earl 2000s. Really sone incredibly fond memories.