Pajamas come in so many styles and designs, there's something for everyone. If you're looking for a classic look, perhaps pinstripe PJ's would work best. Getting ready for a grown-up sleepover with the girls? Channel your "OMG, it's back to high school" phase with crazy colors and polka dots. Whatever the style, make sure it's a good fit for the giftee. (Above, find some sleepwear that you would not be embarrassed to have breakfast in....)
Side note: I know some people sleep in the buff but that is not always appropriate...Say, when Uncle Lou is visiting or the company conference where you have to share a room with the new HR Director.
Extra Idea: Let this be the one gift you open before Christmas so all your family members can wear their new pajamas while opening presents Christmas morning.