Serious Sam

Serious Sam is a series of first person shooter games with excellent cooperative mode, developed by Croteam also known nowadays for The Talos Principle games.

Serious Engine 1

FPS counter

Open the console with ~ key and set the following variable to 1 or 2:

/hud_iStats=1

Serious Engine 3

FPS counter and graph

For compact FPS counter, open the console with ~ key and set the following variable to 1 or 2:

prf_bShowFPS=1

For bigger FPS graph:

prf_bShowFPSGraph=1