If I'm slumming it or going across an international border, it's a Chromebook for me. I picked up a few Lenovo Nxx models for $70 a piece awhile back. Gets the job done, dispoable if need be.

For nicer stuff, our office uses Lenovo Thinkpads, T or X series. Not quite as bulletproof as they used to be, but still better than what Dell/HP crank out, and still have been very reliable for us. We do have a 12" Yoga 900 that gets kicked around the office that's a nice slim computer, about the size of an iPad, but lighter, with a decent keyboard and good battery life. BUT, the Yoga isn't going to be able to take the abuse that the Thinkpads can. I've already had to replace parts on it after a coffee spill.