Klipschorns.
Because they are the best sounding speakers I have ever heard, and because they were basically the best thing that Klipsch was able to design after about 10 years of research, in 1948 - and to this day, beyond the life of it's original designer, they don't seem to have come up with anything better. Are there other speakers that are better? Perhaps. I have indeed heard other speakers that sound really good, but those weren't better, just different, and many of them were over $100k. It may sound like a boring obvious suggestion, but Klispchorns are spectacular, even if they aren't rare. Horn or not, Klipschorns are in the top tier in my opinion.
Because they are the best sounding speakers I have ever heard, and because they were basically the best thing that Klipsch was able to design after about 10 years of research, in 1948 - and to this day, beyond the life of it's original designer, they don't seem to have come up with anything better. Are there other speakers that are better? Perhaps. I have indeed heard other speakers that sound really good, but those weren't better, just different, and many of them were over $100k. It may sound like a boring obvious suggestion, but Klispchorns are spectacular, even if they aren't rare. Horn or not, Klipschorns are in the top tier in my opinion.