The coolest thing in my current car is the big V8 under the bonnet!!!!
But going back to my Astra, best feature (i know it's aftermarket but was simple to install into the car than others) was my auto close windows!!!
Just the fun of leaving your windows open and everyone going 'hey you left your windows open' and i'd walk away as if i didn't care!!! Then one touch and bang all the windows close, i get excited over simple things!!!
Plus the fuel consumption, ohhh do i miss the fuel consumption!!!!