My two favorites:
1) O. Winston Link's famous Christmas Ever recording at Rural Retreat with an N&W Class J making a station stop with church chimes in the background.
2) A night time recording of a UP 2-8-2 running at speed from far off, which then passes under a bridge where the recorder is set up, with a fantastic UP standard freight whistle. This sequence is on side 2 of the famous 331/3 LP "Big Boy".