Besides the '66 Batmobile, this is the coolest Hotwheel ever made:
The '55 Chevy Panel was released by Hotwheels as a First Edition in 2006. It was an instant classic.
The First Edition was released in less numbers than standard First Editions, making it one hot, and hard to find, Hot Wheel.
It has since seen release in a couple other series, such as the silver/flamed Since 68 shown here:
Besides being an awesome, solid, large, mean Hotwheel, one more thing that makes the '55 Panel special, and especially cool, is this:
Pop the back open and slide out the chopper baby!
Now if THAT isn't the coolest thing Hotwheels had done in, well, ever, then I don't know what is. (Besides of course the '66 Batmobile, which is in a class by itself!)