It has to be the shower. Its such a unique experience, and also really does make a big difference in feeling refreshed on arrival. Whilst it may seem like a gimmick at times, it certainly has come in handy on several occasions when ive had to go straight off a flight and into a meeting.

Enjoy the overall experience. If its your first time id let the crew know, as they tend to make a fuss and look after you if its a good crew.