Sayrum mentioned the AKG portable DJ headphone; other than the potential "clamping" effect on those of us with larger heads, I might be tempted to take a chance on them. There's something to be said for not leaking sound in or out while at the office or on the go (which is why I concentrate on IEMs).
But as for 'phones with which I'm familiar -- I have the PortaPro 2's. They're very light, smaller/less obvious than I had pictured them to be, based on online photographs, and surprisingly comfortable and "non-aggravating," considering the metal headband, which works better than I would have thought. The sound is really quite good -- very "big," considering the light weight of the headphones. I can give an unqualified recommendation for using them at home (I haven't tried them out in public) -- use at the office could depend on how concerned you are with appearances ... frankly, they could look a little nerdy ... much would depend on your work situation. But the performance-to-cost ratio is excellent.
The Sennheisers have an excellent reputation and certainly look good -- for a pair of portable, open headphones, I doubt that you could go wrong with them. The KSC75's are supposed to sound amazing for the price, but the "Princess Leia effect" might or might not put you off -- also, I would think the earclips have about a 50-50 chance of suiting a person or driving him/her crazy. I bought a pair for a friend -- I'll have to try them on sometime, to see how they suit me.