The StarterPack object is a service-level container whose contents are copied into all player's Backpacks when the players spawn. It is usually used to hold Tool objects and HopperBin objects, but sometimes LocalScripts are placed in it so that every player has a copy. The StarterPack object is often used as the container for all weapons and other gear items.
Some famous creators put a Anti-DLL LocalScript inside, in which it crashes ROBLOX forcing to close it leaving the place unharmed. There is a bypass though, the user 'Dekot' is working on a code to patch that.