A used Fostex TH900 for sure. Everything is detailed, and the supposedly sharp highs can be tamed using EQ without sacrificing too much of the original sound signature. Female vocals are great, male vocals are decent (U shaped signature so that is to be expected). The bass slams deep into the subbass without that chubby midbass that you would normally fine in headphones of this sound signature. Better soundstage and imaging than some open backs like HD650 and LCD2C.
A distant 2nd place would be the Campfire Cascade. For me, their sound signature plays a bit too safe. Jack of all trades, master of none. Bass has LOTS of quantity, way more than TH900 and THX00 but they are not as tight and can bleed into the mids. L shaped signature (way elevated bass in terms of quantity in comparison to other stuffs).The highs are not so bright, so they can be played safely with poorly recorded tracks.
The 3rd would be the THX00. Its like a TH900 but more V shaped. More annoying highs, more bass quantity and impact (but overall quality not as good as TH900) and more recessed mids.
The 4th would be the Meze Neo 99. The same safe sound signature just like the cascade but a bit worse in all departments.
Comfort wise,
TH900 + Dekoni Lambskin earpads take the first place. Then TH900 + stock.
Campfire cascade has comfortable, thick earpads but that headband is poorly designed and will create hotspot on your scalp.
THX00 + stock earpads are worse than TH900 + stock. Smaller space for ears inside the earpads. Changing the earpads will make the comfort level equal to that of TH900 since their frame are the same thing.
Meze Neo has good headband design but very small earpads/earcups.
Both Cascade and Neo are portables. with portable casings provided. So there's that.