I suppose I would miss his obvious tendency to smoke cigars beyond the rest. Even though I am not a smoker myself, this has become so much of Columbo's character that it would just not fit to strip him of the cigar.
I think I would miss the sometimes irrelevant--but not always--stories he tells about his family. The wife who paints by numbers, the nephew working his way through community college to go into refrigeration business, etc.