Until recently I was using a Lenovo ThinkPad Edge E530 for sysadmin work. It was ridiculously cheap for a ThinkPad, everything worked under Arch Linux and best of all it had a numpad, which I needed. It was mostly sitting on a desk and not moving around much, so the weight and size weren't a big deal.

I just took a look and the newer model E540 can be ordered with a full HD screen (15") which weren't available on the older ones.