[FlyingFungus]

Only one: Denon D2000
 
Only two: Denon D2000 for home, MEE Audio Pinnacle 1 (once they process my warranty and send me a new pair that is -_-...they do sound amazing when the cables work properly)

 

[justhavingfun]

I will be happy with Sennheiser HD600 if I HAVE to choose only one. 
And it will be my trusty Ety ER4 series IEM for my next choice. 

 

[pbeg7]

So.hard.to.choose..

For now, it is probably my ad900x's, but will (likely) change to the HD600's once they arrive.

 

[Svatopluk]

Home: T1 gen2
Portable: MDR-Z7

 

[pbui44]

Only one? Hifiman HE-4.
Only two? Hifiman HE-4 and Sennheiser HD250 Linear.
Why? Because you gave no limit on sources, DACs, or amps and both are guaranteed power-hungry.

 

[gonzfi]

T1 v2 (or v1) because they are the best all rounders ive heard. Great for all genres of music, films and games.

 

[Arniesb]

If one i choose T1 1.1
If two i choose HD800S and TH900

 

[Rearwing]

HE 500 as my only choice
Plus HD 600 as my second choice 

 

[Greggo]

Cool thread and I am in a headphone hobby crisis mode at the moment and completely re-thinking how I am going to approach this hobby going forward.
 
I will add some other qualifiers to my own list so folks know where I am coming from:
 
I want my hobby to be simple, accessible, and uncluttered. Also, build quality and comfort are no longer negotiable. No, it is not about the sound at the end of the day, it is about the user experience at the end of many long days of counting on headphones to deliver a quality audio experience. Portable is a consideration, but readily transportable is a must have on all counts (headphones, DAC/amps, sources)
 
No more desktop amps and no more headphones that require serious or very selective amplifier pairings to achieve their best or near best performance. From now on my headphones must achieve 85% plus of performance potential straight out of decent phone or laptop or sound-card headphone jack, and must achieve 90% plus of potential performance out of a decent DAP or Dragonfly 1.2 or Dragonfly Red (or any other similarly sized/priced DAC/amp of your choice).
 
So for what I currently own, my choices are:
 
Just One - Sony MDR-1a
Just Two - Sony MDR-1a and Audeze EL-8 Open
 
Headphones I have listened to that I will be purchasing soon:
 
The Oppo PM-3 will displace the Sony as the sacrifice in comfort is slight but the improvement in resolution and balance is worth the price increase and substitution
 
The Audioquest Nighthawk will replace the Audeze as I think it is an all around better headphone and the comfort and durability is a good step up
 
Other contenders for me, with my new found priorities in this hobby:
 
AKG K812Pro
Mr Speakers Ether and Ether C
Fostex Massdrop TH-X00
 
Current headphones that might stay in my collection as part of this exercise depending on how I feel after more auditioning, but they struggle without a serious amp:
 
AKG Massdrop K7XX (these will probably go to my son anyways, he wears glasses and loves these even out of his laptop... go figure)
Sennheiser HD700 (these will probably stay because comfort is out of this world, sound is extremely good with EQ cut at 6kHz, and new DAPs will probably drive them just fine)
 
Headphones that I think would be included in my list if on a tighter budget:
 
ATH-M50x (I might buy the new limited editions because they look good, sound good, feel good, and make great "loaners" to friends and family)
 
Now I have to get ready for some separation anxiety as I get ready to sell about a dozen headphones and my desktop rig...

 

[ubs28]

If I only had one headphone, what should I get? For all uses...just one.
 
- Shure SE846
 
And as a second question: If I could only have two headphones, what would I get?
 
- Sennheiser HD 800 S (home use)
- Shure SE846 (portable use)

 

[derbigpr]

T1. The only real "all-round" headphone I've ever owned or tried, and I've tried pretty much everything on the market. It's the only one that wouldn't make me feel like I'm missing out on something or getting too much of anything in terms of sound, it's transparent enough to be a reference headphone, but fun enough to be a main listening can. It's comfortable enough to disappear from the head, and built well enough to last forever.
 
HD600's would be on 2nd place, but their lackluster soundstage, boomy upper bass, poor bass extension and somewhat congested sound in comparison to the T1's would already prevent it from being a great all-around headphone....which is the reason why I said the T1's are the only real all-rounder I know of.

 

[ubs28]

How can the T1 be an "all-round" headphone when it can't be used outside?

 

[Vigrith]

Orpheus.
 
If we're talking reasonable, Ether C and HE1K.
 

  How can the T1 be an "all-round" headphone when it can't be used outside?

 
Not everyone wears headphones outside, a lot of people work from home nowadays and/or can't (or doesn't want to) wear headphones at work. Travelling (both short and long distance) by car with a good integrated sound system negates the need for hps while commuting, plus for a lot of us being outside implies company be it spouses, kids or just friends. That leaves home use wherein the fact the headphones are open is mostly negligible. The definition of an all-rounder can then shift, for you it factors in utility (ie. portability) whilst for him it seemingly doesn't - he is right too, in my opinion the T1s are apt for all music genres, movie/series watching as well as gaming making them a good all-rounder.

 

[Arniesb]

How can the T1 be an "all-round" headphone when it can't be used outside?

I think he was talking about sound only... I personally use my headphones at home only, maybe he also?...

 

[Star2806]

Tascam TH-MX2/Prodipe 3000 closed headphones, as they have a nice warm and neutral sound with quite good sub bass.  I wrote a review about them here on headfi.
 
Portables:  Philips FX5m closed headphone, they have a fun bassy sound signature with clear highs.