320 Smith St Brooklyn, NY 11231, USA
The northern entrance to the downtown Coney-Island bound F/G train always floods when it rains, making a puddle several inches deep that's uncrossable without soaking your shoes.
Fort Hamilton Parkway And Prospect Expressway Brooklyn, NY
To get to the Fort Hamilton Parkway F/G station from Fort Hamilton on the west side of the Prospect Expressway, one major access route is a path that goes under a bridge that crosses the expressway. Every time it rains, the passageway floods, leaving an enormous puddle that is impossible to cross. This has been going on for a very long time: http://www.kensingtonprospect.com/news/dont-forget-your-flippers