I would prefer ID, Code, Description where ID is identity int and Code is unique.  Not sure I care if description is unique although I can see that as a possible advantage.  One issue with all data is to apply the 18 inch rule.  Whoever is 18 inches in front of the monitor has to be responsible for the data that is input.  Lookup tables should be as static as possible and therefore any additions to a lookup table need to be made very carefully.