I tend to want engines I have a connection to. The one I have had the most experience with is actually quite obscure, there isn't anything remotely close to it out there model-wise. Funny thing is it's just a little Alco-Cook consolidation.
her size makes her unique, if I remember right engine and tender combined weigh just 90 tons, she is not superheated, and has walschearts (sp?) valve gear and no power reverse. Built in 1920.