I was going to say the moment when I slip through the tunnel and see Main Street for the first time. (I'm a huge Main Street nut, even if they have got rid of all the cool things, like the Penny Arcade.)
However, I have to say the first time I really get itchy is on the drive in, passing the signs. Nowadays I do it by bus, but I still remember driving in, tuning the radio station, etc.