Yes, Ford GT: good future investment.
One that I believe will be a great future investment is the 2006 Mitsubishi Evolution IX. One year only design, and the final year for the "original" Evo platform. Low production numbers. Strong racing (rally) heritage, and an even stronger worldwide cult following. In the US at least, the best performing Japanese car of its day.
Trust me, we'll see a low mileage Evo IX on Barrett Jackson in 20 years bringing big money. Too bad I sold mine a couple of years ago.
Anyway, back to the ZR-1; I really believe it's going to be a blue-chip Corvette one of these days. It's not super low production numbers, but it's rare enough, and the novelty of the DOHC engine along with the period heritage ("King of the Hill", the 24 hour 175 mph endurance run, etc.) make it a special Vette, and special Vettes are the ones that appreciate over time. As always, condition and mileage will determine overall value, but I do believe that values have bottomed out.
Sure, if you bought one new, you have a long time to wait to even break even, but if you buy one now, I don't think you will lose much money, and have a better-than-average chance of making money.
I'm ready to put my money where my mouth is and buy one soon.
My dilemma is: I want to drive and enjoy it as well, not just have it sit in a climate-controlled garage somewhere...