For just over two weeks, the Beyerdynamic T 70.
My poor Sennheiser HD-650's are getting lonely by themselves on the shelf. They're definitely not used to it.
Pretty much an even split between"
Larocco PPA => RS1
Millet hybrid => K701
Thinking about adding a DT880 600 ohm for my Earmax OTL... I have never really used this amp to its fullest.
At work, the LCD-2 direct out of an iPad (have them on now). Don't laugh - they work surprisingly well out of the humble iPad. Better, in fact, than from some amps I've owned. Perfect for low volume listening. Try it, you'll like it. I'm going to put a scope on the output to see when the iPad clips, but I keep it low for long listening sessions. Oh, the travel case is the best thing about these headphones - everyone thinks it's a lunch box. Use it every day.
At home, the Stax Lambda Pros while at my desk, with the HD650 or LCD-2 from the Lyr when sitting in my poolside window seat reading - very relaxing. The HD650 aren't getting too much time lately so it's probably time to pass them on. They are so very comfortable that I hate to get rid of them.
I don't have much of a collection (the other cans being a vintage Sansui SS-20 and a Philips CitiScape Uptown), but it's easily my Stax SR-Lambda (Normal bias). Comfortable enough to wear for hours on end, and an atmospheric presentation that I've only had out of Lambda variants thus far.
That said, I got the lucky opportunity to audition an HE-400 for a week without paying full price first, and you can bet I'll be taking advantage of that while it lasts. So far, I'm liking it quite a bit, though I wouldn't trade my SR-Lambda for it. Comfort isn't quite as good on the HE-400 due to small cup size, though it's still better than a lot of other headphones.
My answer is... interesting. :-)
Sennheiser PMX-90. Bike 40 min/day x 5 days/week = 200min/week.
Audio Technica W1000X and W3000 when listening at home.