Concept car in your garage?

I've been thinking about this for a while and wanted to know your thoughts. So here's the question:

If you could have (and drive) a concept car that was never made, which one would it be? So to make this a bit more interesting, let's add some categories:

1. Box/City car/Other
2. Supercar
3. Luxury
4. SUV

I'll reveal my picks in a bit.