Grado SR-125
The Grado SR-125 headphones need no introduction.  Honestly, I am not even quite sure why I am writing this.  If you know audio, you know Grado.  If you think of Sony or Bose as HiFi...well...then you clearly live in a hole or just need an education from one of your friends.

I received my Grado headphones as a Christmas gift.  I use them as my backpack headphones for listening to on the bus and around campus.  I decided to get the SR-125s because they are not terribly expensive, typically around $150, they are durable, and they provide very high-quality sound.  The one disadvantage of the SR-125 is that they have an larger 1/4" adapter as their only output option.  In my typically portable usage, I am using a mini-jack.  So, as a result, I am using a Radio Shack gold-plated adapter from 1/4" to mini-jack for input to the headphones.  This seems to be working very effectively as a solution.