The best car I've seen is an F40 which I sat in. It was at a car dealership here in Calgary for a fathers day attraction. They had the trunk/hood open and the engine is absolutely so interesting to just stare at for hours (if they'd let me!!)
Yes, I am happy that I am able to say that I have seen a McLaren F1 in person! It was at the CART race at Laguna Seca in 2001. Here are a few pictures...
Never in real life, unfortuntely. Not counting Auto-shows, my best car sighting would have to be a Lamborghini Contach, which was at a local McDonald's. And I've sat in a 2002 Porsche 911 Turbo.