'91 Toyota MR2, bought back in '96 for $10,500. Nearing 267,000 miles now. I've been told a couple times when I got replacement parts recently that I got the last part in stock in the country (brakes one time, ignition coil the next)... Odd, while this is a very limited production car, all the '90's Celicas used the same brakes & ignition system... I've replaced sheet metal specific to the car and that's been easy to get. One of these days I imagine it'll need something and there will be none left to be had though.
'95 Mitsubishi Eclipse, bought in '02 for $15,500. Sitting around 130k miles or so. Can't remember anymore. Haven't seen it in weeks. It's stuck on the lift at the shop with a failed wheel bearing. So far they've been unable to locate any replacement wheel bearing cups for it, and the used ones they've located have been trashed worse than mine. Might be the end of the road for it. Possibly will have to throw it back together, limp it home, and then start parting it out. While they made this model through '99, it appears that having a limited slip rear end is the sticky part. Those seem to have been very rare. I guess parting it out isn't the only option, I could try finding a decent used open diff rear end and swapping it in since everything else on the car is *very* readily available...
'94 Suzuki Katana 600 (motorcycle). Bought a few weeks ago for $1. Put about $300 into it, and have been riding it around already. Needs a front tire real soon, and brakes eventually, but even after that I'll still be in for only 10% of what a brand new 300cc bike costs. Factory support is excellent. I place an order online through a local dealer and the part is there 2 days later without fail. Parts book still lists parts for bikes going back a decade before that!
Looking like motorcycles might be the best way to go for a very long term vehicle. If you must have a car, stick with Toyota or Honda (general case), or get an American muscle car (not terribly mustachian, but those old V8 cars always have parts available) as those have excellent long term support. American "regular" cars seem to have quite poor long term support, as does Mitsubishi (from what I'm told while trying to find the part I need, but I've gotten other parts fine)... Current value of all my vehicles is basically the $500 scrap value now. :-)