I've owned a pair of Koss Portapro headphones for five years or so - excellent little headphones - great sound, good comfort, quite portable. (On the minus side, they look a little geeky, and they're not cheap for little headphones)
One speaker cut out a few months ago. Koss has a lifetime warranty, so I sent them back with a check for $6 - and, voila - I now have a new or reconditioned (I can't tell which) pair of 'phones.
Thanks Koss! Great customer service!