Going off-registry for a wedding gift is not for the faint of heart. If you’re considering making the leap, you’ve got two factors to weigh: How well do you know the couple and, more important, are you a natural at gift giving? To help with the latter, we tapped six pros on wedding presents, from etiquette experts to globally recognized event planners, to share their best advice. These are the unique, and pretty much foolproof, gifts they recommend.