Most comfortable headphones

Sennheiser 6xx. I have a dozen headphones, these are the most comfortable by far and sound great. 

Grado, they range from $80 on up. Light weight. They are all open back so not good for noisy places, just FYI. 

I have found that the Brainwavs leather upgrade pads really increase the comfort of headphones. (totally better than most stock pads).

Other than that, some headphones have a tighter clamp spring which some people complain about.

It depends on what kind of headphones he likes. If Bluetooth, you can look at Sony I have had them for 6 years, and I do not want to change. Along with them, I used wired headphones for the computer, but the wires are constantly getting tangled. And Bluetooth doesn't break as often.

It depends on your friend's requirements for headphones. If he likes headphones, he could choose Sony and Beats. If your friend likes bone conduction headphones, he could choose Naenka and AfterShokz.