My husband and I want to experiment with acting out different fantasies, a robber/rape fantasy in particular. Has anyone done this and how did it work out? Is there anything we should discuss before attempting it? A safe word will be needed, right?
Thanks!

A good place to look for advice would be http://www.janesguide.com/ -- the review index is full of all sorts of sites with advice, along with erotica that may inspire a fantasy to act out.

Personally I think you should discuss it with each other first. In particular you need to know what things would turn each other on and what things might be potentially dealbreakers.

For example he might think robberies involve wearing a stocking mask but it might be that you think he looks silly in it or it reminds you of something unsexy.