Bought a PC case last year which has a green power LED. It's infuriating how bright it is in the dark, and despite being placed below my desk I can still see it e.g. when playing a game in the dark. I wrote a message to the manufacturer and suggested that this is pretty annoying. They were quite dismissive and replied that it's "impossible to make it darker". I'm not an electrical engineer but I'm positive even I could accomplish that task with some additional resistors.

Edit: I should also add that the LED is part of the power button, so it's not so simple to just tape over it. If I want to play in the dark, I put a piece of paper / cardboard on top of the PC.