Instructions
Join a game of "Roblox."
Download and open Cheat Engine (see Resources).
Click the icon that looks like a flashing computer. It's located in the upper left hand corner of Cheat Engine.
Click the Window List button, then locate the icon labeled Roblox [game name]. Inside the brackets will be either the name of the particular Roblox game you're playing, or Place 1, depending on how the game was built.
Click the Memory View button, then use the search function in the pop-up window to find Torso.
Right-click the Torso file in the main window of Cheat Engine and left-click the "Make Page Writable" option.
Right-click on the first number next to the word Torso in the main window of Cheat Engine, then choose the "edit" option.
Type 01 into the box, then press OK.
Reenter the game. Every player, including yourself, will immediately start dying.