Everyone has their own "benchmark" models. Models that set a milestone for them for various reasons. I haven't heard any of the following mentioned, but may have missed them.
For me: 1) Midwest Lil' T-- This was my first sailplane. Not a completely pure sailplane as I launched it with a Cox .049 on the front. Hundreds of flights as a kid with this and hooked me on sailplanes. 2) Windfree-- What a great plane. There is so much I could say about this one. 3) Hobie Hawk-- Never had one but it seems to me this was one of the first molded planes. Totally out of my league at $149 retail at the time. Darwin N. Barrie Chandler AZ