Sennheiser HD-280 , probably the best bang for the buck out there, but you do pay a dork tax (they are not the best as far as looks).
I use Shure E5s, Pioneer HDJ-1000s, and HD-280s for my live and studio mixing/DJing/producing/listening.
The Shures ($$$) isolate the best, and sound the best, but it hurts to insert and remove them a lot (not the best for DJing), and often, the block out too much ambient noise for the environments I am in. The Pioneers ($$) look the best and isolate very well. They are a bit bass heavy, so I default to them a lot for lazier DJing (and b/c they look better, yes I am vain like any other live performer in history...). The HD-280s ($) are the most comfortable, and isolate well while providing an accurate representation of the sound you are monitoring. They are also about $80US. There is reason why you will see them everywhere... I have one pair of the Shures, two pairs of the Pios, and 6-8 of the 280s at any given time (we use them for radio/band production, general listening, etc) I would highly recommend them as your first set of serious headphones. Get a pair of monitors to complement them before you start buying $200-500 sets of headphones.