I've posted a number of times that I'm an Sennheiser HD600 guy through and through, but for kicks I'll throw another one out there: check out the Superlux HD668B. Incredibly cheap headphones that sound pretty amazing. I mean, they sound REALLY good!
For $35.
They aren't as open and "airy" as the HD600, but they are louder and they pair better with a lot of amplifiers. For that price, you can buy one for a back up, and a 2nd pair as its backup.
My favorite headphones are the Sennheiser HD8 DJ (closed), which I use to prepare the sounds. They are not much used by guitarists, perhaps because they were born for DJs, however, in my opinion it is much more flat than many others. Then I also use the Beyerdynamic DT 880 edition 250 ohm (half-open) which, if used with the addition of the Sonaworks References 4 calibration software, may sound almost like the more expensive Sennheiser mentioned above.
