A Toshiba T1950CT that is somewhat of a time capsule. 200MB HDD, 486DX2-40, 8MB RAM - with what seems like its original installation of DOS 6.2 and Windows 3.1 from 1993/1994 on it, whilst it seems to have been parked in 1997. There's even some scientific studies into sexual health in Zambia on there!
It has its flaws though; it needs a proper clean, the belt in the floppy drive has failed I believe (motor whirs but that's all), the power jack is a little flakey (hopefully it'll be happier with its original charger when the seller finds that!) and there's a single stuck pixel in the screen. But the HDD sounds to be in excellent health, and although it had quite a lot of lost clusters, scandisk did not report a single bad cluster. And when I don't knock the power cable, or get it in the right place - it's rock solid stability-wise.