The Hidden Mod Redux
Team Fortress 2 - The Hidden Mod Redux
Never heard of this mod before? It's based on The Hidden:Source mod - https://www.hidden-source.com/. Basically a variant of One person vs Everyone else(like vs saxton hale). On the red team you have players(called team IRIS) with no special abilities but you have the quantity. On the blue team you have The Hidden. It's a permanently cloaked spy, only revealed when attacking or using his abilities. The objective is pretty simple - kill the hidden before he kills you.
More information about the mod can be found here: https://forums.alliedmods.net/showthread.php?t=284286