Sandbox is the default gamemode of Garry's Mod. You can build anything in it.
This gamemode features a spawn menu, by default opened with Q that has taken some change over its time. Pressing F1 will enable the model search. The left part of the menu allows its users to spawn ragdolls, NPCs, entities, vehicles, dupes, and props. The right part of the menu allows its users to configure the Tool Gun, server settings and player settings
Each gamemode in Garry's mod is allowed to have its own custom scoreboard. By default, the scoreboard displays a players username, number of kills, deaths, and ping, along with an option to mute users in voice chat.