Virgin have always been good with the humour, a few that I've heard and remember:
"Ladies and gentlemen, welcome to Brisbane ... your baggage will be available on carousel 2 sometime tomorrow"
"Take note of your nearest exit which, like a stalker, may be behind you"
"Your life jacket is equipped with a whistle to attract attention, and a light should you wish to continue reading"
or my personal favourite:
"If gas masks fall from the ceiling, pull down on the mask firmly, stop screaming, and fit the mask before helping others"
Also (which was quite surprising) was a Qantas CSM on an international flight. He would have been in his 60's, with a very proper English accent, and he said "Ladies and gentlemen we'll be dimming the lights on take off to make the crew look better, so there is a light switch in your armrest"