Headphones on the Subway
It drives me absolutely nuts when I am sitting halfway across the subway cart from someone, but can still hear the sound coming out of their headphones. Thanks buddy, I appreciate that you are concerned that I am not listening to something, but if I wanted to listen to music I would put on my own headphones.
The only thing worse then sitting halfway across the subway cart from these offenders is sitting right next to them.
Half the time, I want to tap these people on the shoulder and start explaining all the bad things that earbuds at such extreme volumes do to your hearing in the long run, and then politely ask them to lower the volume for their own sake, as well as mine.