http://www.urbandictionary.com/define.php?term=hipster
Like it says, hipsters wear skinny jeans, ironic tee shirts, cardigans, thick-rimmed glasses, and frequently, headphones. However, not just any old pair of headphones will suffice, they must be hipster headphones!! I'm not talking some boring old pair of Sonys or Bose. No, I'm not even talking the "cool" Skullcandy headphones, these are way too overworn. You want something UNIQUE, but also something obtainable.
If you can find a pair of vintage headphones that still work, then definitely go with those. You can't get more hipster than vintage. If you'd like a newer set of cans, but don't know where to look for them, I suggest any of the new WeSC headphones. Here's an example from Amazon.
They run between $35-100 (depending on model) and look great!!!