manhattan portage debranded 'cornell' messenger
i've owned.. a lot of shoulder bags. expensive leather ones from ralph lauren, cheap-o ones from jack spade, but my favorite -- by far -- is this black messenger from manhattan portage.
it's lightweight, totally nondescript, has a great pocket configuration, is fairly waterproof, and fits a 13" laptop with case perfectly.
i've had this one for maybe four years? it's the second one i've owned. with the first, the shoulder strap started to tear off, and the company replaced it no questions asked. by this point the black cordura has faded a little, and i think it looks great.
i also own the standard filson 256, but i actually like this much better. with leather/canvas bags i always run into weight issues, but this has the perfect combination of durability and heft.
it originally came with an ugly red manhattan portage badge on the front, but it took maybe 10 seconds with a seam ripper to remove it.

