JBMod is a mod that is the predecessor to Garry's Mod. It focuses on setting up ragdolls in sexual poses.
From the official site:
"JBMod was originally made because the nerds on HL2World wanted to get back to making sexual poses with the ragdolls in Half-Life 2, which they weren't able to do anymore since the physgun had been removed from the final game. Both prior to the release of Half-Life 2, and after the release of JBMod, just about every screenshot involved Alyx Vance."