New York Subway
Again, I was shocked. The subway is an iconic New York thing.. but again has not seen the kind of improvements/overhauls neccessary to bring it to the 21st century. While New York maintains their subway, I think they also take it for granted. It is proof to me that frequency and line-density (many lines), trump rider comfort.
Unlike London or Paris where I was quite happy to duck down to take the metro or the tube, I ended up using the subway only to get in and out of town. There is no air circulation, there are rats, it is gross.