As we know there are thousands of things you can do in Garry’s Mod, which includes mini-games.
That’s the Garry’s Mod wiki link to a list of mini games you can play in Garry’s Mod Sandbox.
I have only one to share as I am not creative.
Make a target on the wall using your rope tool. Make it very large and visible.
Make smaller circles or squares inside of your target using the rope tool.
Spawn a sawblade.
Shoot sawblade at target with Gravity Gun.
Play with friends
What Gmod mini games keep you occupied FP?