Great thread!

I have so many wow moments, but the first that comes to mind is an upgrade from a jr. suite to one of the signature suites at MO Las Vegas which the receptionist informed us about only when taking the lift to the room. A huge suite with floor to ceiling windows including bedroom, bathroom, working area, dining room, hall, our own bar, kitchenette and a large living room. At the bar counter a display of complimentary treats and drinks, including special treats for our son. Fantastic! (especially knowing how rare upgrades are at this hotel).

Will think of more later.