Snowfall on CS:GO
You will need https://github.com/K4ryuu/Karyuu-Library if you want to compile it by yourself.
Screenshot: https://i.fastguard.ro/csgo_N7kKnFOj8O.png
Usage:
- !snow - toggle on/off (saved in clientprefs)
All credits goes to the author mentioned in the plugin source code. https://forums.alliedmods.net/showthread.php?t=174790&page=10