Admin Mod

Admin Mod is a Metamod plugin that allows you to administer your Half-Life server while playing the game from your client console. Multiple administrators with different permissions can be set up, each with their own password. You don't need to give your server's rcon password to all your administrators anymore.
It also supports scripts written in the Small programming language that add new features to the core program.

Features include:

Admin Mod is compatible with all Half-Life based games that are compatible with Metamod and runs on Windows and Linux/FreeBSD operating systems. It is currently used on over half of all Half-Life servers active on the Internet.