I really enjoy The Conspirators, so if Last Salute had been the final episode, I would have missed that one a great deal. Such fun.
I enjoyed all of the Season 6-7 episodes, except Old Fashioned Murder. That was rather dull, so it wouldn't have been missed on my DVD player. Of course, 'Rosebud' and the word game would be a terrible loss, along with Lt. Lucerne and Abigail Mitchell.
For the newer episodes, "Columbo Goes to College" and "Columbo Likes the Nightlife" (which actually is the final Columbo episode) would never have arrived and that would have been a shame. Columbo Cries Wolf was also a very enjoyable watch.
I agree with Columbo goes to college. It was worth it to me to see those two punks go down at the end of that episode. They deserved everything they got and then some