Any Non-RP Gamemode Suggestions/Ideas

I've recently been getting into coding, especially GLua, I think I'm ready to take on the challenge of making a custom gamemode, but I have no creativity when it comes to things like this. What are some gamemodes that you guys would love to see in Garry's Mod? Please, no roleplay suggestions! If you have an idea, explain it with detail, just saying: "Custom DarkRP Ripoff Edit thing" doesn't give me enough