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:
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/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:
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prf_bShowFPS=1
For bigger FPS graph:
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prf_bShowFPSGraph=1