Pie Jumping
An incredibly blatant and obvious form of cheating that anyone can do, but most refuse to do so, often because of an unspoken gentleman's agreement. Anyone who does it is frowned upon and often targeted and insulted.
Pie Jumping is named for a technique in the Roblox game Plates of Fate where a player uses the pie tool to maneuver around the game and utterly invalidate the bottomless pit. It is almost universally considered a form of cheating among players, yet the developers refuse to do anything about it.