I'm more concerned with what to give a cigar virgin or seldom smoker. If the goal is to give a newbie a cigar he'll enjoy and finish and not waste, and that won't make his head spin, then we're talking mild. Gispert Natural, Cu-Avana, just think of cigars you thought were too mild for you but not bad otherwise.
As for regular smokers, play it safe with a medium bodied cigar with no bitterness. Romeo and Juliet come to mind.