I like the Union Switch and Signal Co. style "R"/"R-2" (as well as similar models like the style "N") vertical colorlight signals. I also like other antique and vintage signals such as searchlights, etc.
One thing about antique signals is that the cases of many signals were made of solid cast iron. Not the aluminum or plastic that modern signals (modern signals are often Safetran colorlights) are probably made of. Just think of the effort it took to haul those heavy cast iron signals up to their mounting spot on ground posts, gantries, cantilevers, etc., and mount them back in the day.
Regards,
Zachary.