Action Half-Life is a multiplayer modification that focused on cinematic gun-play. The game featured maps by Hondo, who was famous for incorporating massive puzzles in to his levels. These sprawling mysteries are explored by YouTube user bobandalot through narrative walkthroughs uploaded to his channel. [more inside]
Apparently, a lot of the custom maps for the Half-Life 1 mod Action Half-Life (download links here), especially those done by enigmatic mapper Hondo, had enormous hidden areas that in some cases dwarfed the actual level. Rock Paper Shotgun has a NGJ-style account of an effort by a group of people to unlock the secrets of one of Hondo's most infamous maps: AHL_5AM.