A thirteen year old Compaq Armada M300. (Btw, for being 13 years old, it's the thinnest laptop I've ever used, thinner than my current one!)
I installed Lubuntu onto it and it worked pretty well.
12.1 inch screen
256MB of Ram (Top of the line config option)
6GB Hard Drive
It lasted all of these years and still looks new (it has a full metal case, and it's only 3.4 pounds).