Although to be honest, the first time I drove an E93 M3 - I knew within the first minute I loved it.
I have driven numerous fast cars and always come away a little bit cold afterwards, especially if I only drove it 30 minutes or an hour. I've gotten this reaction after I drove a CTS-V, C63, 911 turbo, IS-F, etc. All marvelous and fast - but none gave me a visceral and physical reaction.
The M3 certainly did. I remember the first time I test drove one, as soon I pulled away from the dealership onto the main road, I had it in M mode - floored it, and on the first shift on the higher rpms I felt excited and chills! That is the sort of reaction I am looking for. Everything felt so sharp and neck-snapping fast, in terms of throttle response and shifts.
The Z06 is similar too, and the Cayman S as well - which is why I am comparing these 3. At the end of the day, this is my "exciting" and fun car to drive, so I want something with emotion.
It's not exactly about how fast they are - but how they produce their power. A Z06 is much faster than either, but I think both of the other ones produce their power and handling in such a marvelous way that you don't even think about the speed.