I also think grail pins are ones that have been out for years and something hard to find in decent shape. I have a MET pro and really like it but it's not like a grail pin. For me, one of my grails was TZ. Played it back in the day and always wanted one. Avoided buying it early in the hobby because of cost and concerns of maintenance. I had an opportunity to get a fairly nice one early this year and took the plunge. Probably paid too much especially since it needed some work. No regrets and really feels special to own. My other grail would have to be Funhouse. Another game I have always enjoyed for whatever reason. Like to get one but not sure it's really worth the big money they go for now days. So many other great pins out there.