Serious Sam the First Encounter & Serious Sam the Second Encounter.
Grade: C / A
Serious Sam has two different versions. To disable the hud and make the crosshair transparent in the original version, add the following commands to the Scripts/Game_startup.ini
hud_bShowInfo = 0;
hud_bShowWeapon = 1;
hud_bCrosshairColoring = 0;
hud_fCrosshairScale = 1;
hud_fCrosshairRatio = 0.5;
hud_fCrosshairOpacity = 0.0;
hud_bShowPlayerName = 0;
If you're playing Serious Sam HD (the remake of Serious Sam The First Encounter & Serious Sam the Second Encounter), the option to disable the hud and crosshair are natively built into the game and can be selected in the menus (advanced options, if memory serves).
Serious Sam HD - No Hud