A staple of of early D&D is the "1 in 6" or "2 in 6" chance for surprise, finding secret doors, and so on. Recently, some of the retro-clones, mostly noticeably Lamentations of the Flame Princess ...
For those unfamiliar with the concept semi-diceless gaming is only having the players roll the dice. It's used in Cinematic Unisystem and the old (and now free) game Legendary Lives. I'd like to ...