zblock

zBlock is a server plug-in for games that run on the Source engine, like Counter Strike: Source. It is mostly used on ESEA servers and attempts to level the playing field by enforcing CVAR values on each client. It also locks certain server variables, such as maximum player speed in an attempt to nerf bunny hopping, and prevented clients with altered game files that were not detected by Valve. It was famously destroyed by a Counter Strike: Source player Phoon when he published the video "Phoon too much for zBlock" in which he demonstrated his amazing bunny hopping abilities despite the zBlock nerfs on it.