Sennheiser PC 350 SEs - had them for a couple of years and they are the best headset I've ever owned in many years of gaming. They are 150 Ω though. so the only real complaint would be that most sound cards cannot drive them properly. However, I just got a O2 headphone amp from Mayflower Electronics and fixed that.
Just quit playing TF2 a few minutes ago to let my brain decompress from excessive Metallica/Pantera + heavy minigun firing. I'm banking on technology to reverse the permanent hearing loss one day when the time comes.