I've just been reading about some great ideas for flavouring your chocolate fountain.
When you're creating your chocolate mixture you can add in spirits and liquers.
Obviously if you're adding alcohol then you can't let children have any chocolate fountain so you'll have to restrict it to grown ups only. Which isn't a bad thing - the less sharing the better.
My top things to add would be rum, kahlua, and amaretto.
But you would have to consider who else was going to part-take. Only use one, else you'll get a horrible mix of flavours that'll cause wastage!
You could add in a drop of whiskey too if that is your favourite tipple.
Of course you could also serve drinks with the fountain and allow people to enjoy the flavours of booze and chocolate together.