For the year 2007, in honor of the 125th Anniversary of the Gotthard Pass route, SBB Personverkehr is offering cab rides over the route from Arth-Goldau to Locarno, Switzerland. The ride is on one InterRegio train in either direction and requires advance Reservation. Further details can be found here;
This is an extremely scenic route that includes a double Horseshoe curve and 5 spiral tunnels, along with lakeside running. It isn’t cheap however.