Hm… There are a few contenders but I will go with tank, my ThinkPad X201 Tablet. It's the first thonkpad I got, it's the one that made me switch to Linux full-time, that I used through most of my programming studies, that traveled with me the most of all my computers. I still regularly find myself appreciating it, more than most of the things I own. Maybe not as much as my blåhaj, but that's not on my desk.