As we are conducting our list of Essential Free OSR 3 Packs I thought I ask: "Which RPG product has been the most influential on the OSR and why?" I ask, because I can't think of a single one - I have a handful.
Castles & Crusades, as it opened the door that led to the OSR, even if it didn't know it was doing so at the time.
OSRIC, which firmly planted the flag to which other retroclones followed.
LotFP Weird Fantasy, a game that showed you could be true to your roots and still change things up. It also showed the importance of high quality art, and pushed the line of what's considered acceptable in RPG art.
I guess each one represents a different stage of the OSR for me.
Look at that, I asked for one anser and I gave three ;)
So, what are your thoughts?