I chose Main Street Electrical Parade. I listen to the soundtrack and I feel like a kid again. Plus, I miss the spinning turtle, bee, and snail that used to come right up to the crowd and 'talk'.
Away from the list, I would have to say I'd like to see FW returned to its opening day glory- i.e. FWRR, River Country, and the prairie dog family over at the Tri Circle D Ranch.