I'd suggest anything that has a rubber earbud-stylee seal on it to keep out external noise*. Judging by the amount of leakage from the headphones of the kids (or older) on the train, their ears are gonna be seriously fscked in not many years. As it is, I've got a degree of tinnitus from several years of using an mp3 player (with aforementioned earbuds) at modest levels, before that I used bog-standard things for a short while, but the volume I had to use in any noisy environment (bus, and to a lesser degree, train) meant too much volume - and that wasn't even at a level anyone else would hear it much.
Even with rubber earbuds I have to resist turning it up a tad when walking nr traffic.
(Probably going to lots of metal gigs and a short spell in a band with a noisy drummer hasn't helped, tho'...a mate with similar listening preferences has tinnitus that's probably quite a bit worse..)
*sits back and waits for complaints of 'you can't hear the cars around you..'
