The year was... I dunno, 2010 or so? I was playing GTA IV and had an idea. What if we had a deathmatch mode where the entire map was used, there were no player or weapon blips, and everyone only had one life? I told some people about it and they seemed to think it was a bad idea, so I sort of forgot about it.
But holy crap, I could be rich right now if they just gave me positive feedback and I could have been the one to invent the battle royale genre.
Has anyone else come up with an idea before it eventually became a reality for someone else?