I've never jumped off a bridge... What about you? "I've never..." is actually a drinking game, but it can also be fun without alcohol(if you are too young, which you probably are since you're throwing a slumber party). OK, let's take a look at how you play it...
It's simple. One players starts by saying "I've never..." and adds a statement, something like "...made out in the school bathroom". Then all the people that actually did it, have to do something, depending on the version.
In the drinking game, everyone who had done what was stated has to drink, take a shot or a sip.
In the alcohol free version it's the same as with alcohol, except you take a sip of a non-alcoholic beverage. You could also replace the drinking with some other activity, like eating gummy bears or whatever.