Valve has added tons of game modes here and some of my favorites are Trouble In Terrorist Town where you can be a detective trying to find criminals who are killing people. Do not worry, as there are many other games that are made to be played just with what Garry's Mod is offering you.
It is worth noting that some may require you to own another game such as Team Fortress 2 for example in order to play them. Garry's Mod has a very robust set of multiplayer modes that will keep you busy for a very long time.
