Public tash cans in general. I know the way NYC handles trash is unique to them among American cities. But every time I travel to a different American city, especially on the west coast, I'm always annoyed at the lack of public trash cans. Portland Oregon and San Francisco are particularly bad at this. I wouldn't be shocked if their reputations for being dirty was directly tied to this. In DC/Silver Spring/Alexandria/Arlington etc, the commercial districts and major roads have public trash cans basically on every block, on both sides of the block, and on every bus stop. I always notice it when I travel to a different city and I have trash and I go to where I expect a trash can to be but nothing.

I was in Portland recently and had a candy wrapper I wanted to throw away. I was on a major commerical street, and I had to walk so many blocks to find a single public can, and even then, I had to cross the street to use it