Back in the day I had a ton of fun with the Spookshow RPG by Clockworks - game where you play ghosts working for the CIA. A quick glance online tells me that the game can be had for a steal these days.
Like so many others in this thread, I've been gaming since the 80s. But, the time that I have to completely write a campaign from the ground up has shrunk considerably. This means that if I want to run a game, I require one that has good campaign length adventure support, and has game mechanics...