fps_max
fps_max is a console variable available in all 
GoldSrc, 
Source, and 
Source 2 games. This is a ConVar where you can define your frame rate limit. It is recommended that you limit it to the refresh rate of your monitor (or slightly above its refresh rate, like 120 FPS (doubling 60Hz refresh rate), to make mouse input more responsive), because any frame rate higher than your monitor's refresh rate will be wasted, turning those frame into motion blur which could cause the monitor to have screen tearing issues and causing the systems to make coil whine noises (can be heard inside the motherboard or the audio output) due to higher power draw. Limiting framerate however, may cause mouse input to feel less responsive.
Furthermore, having more than around 1000+FPS in a Source games (or 100+ in GoldSrc) will cause timing-related issues (such as the game running faster than normal) and potentially causing the game to stutter (or cause the servers to teleport you back where you should be)[1].
Note: Default: 300 FPS, 400FPS in 
Counter-Strike: Global Offensive and 
Team Fortress 2 branch.
Note: Using 
VSync will cap the frame rate to your monitor refresh rate, which will prevent screen tearing, however this can increase input latency.
Note: Using value 0 disables the FPS cap in Source/Source 2, while in GoldSrc it will make the game run at 1 FPS.
Note: On listen servers, going above 1000 FPS may cause pseudo-speedhacks, where time seems to have sped up. It should not happen on dedicated servers.[confirm]
References
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