I will comment on some of your choices, then tell you mine:
(1) Any Old Port-good episode, but the plot and clues are actually pretty lame. Donald Pleasance is outstanding in taking a poor story-line and still making a very entertaining episode. Also Gary Conway was one of the best victims.
(2) By Dawn's Early-excellent story, but Patrick McGoohan's performance is not as good as the one he did in "Identity Crisis". Still, I agree that it is very good.
(3) Troubled Waters-agree, excellent episode
(4) Candidate for Crime-also, very good. Jackie Cooper is excellent as the slimy politician. I also love the scene where the Italian dentist goes on and on about Italians and the Mafia-this took a lot of guts for the writers and producers to put on the air in that era.
(5)A Matter of Honor-similar to "Any Old Port". Ricardo Montalban is super as the bad guy, but the story is ridiculous. Still, I enjoy watching this one.
(6) The Conspirators-my favorite of them all. I like the political intrigue and Devlin's efforts to get ahold of weapons all the while Columbo is chasing him. Clive Revill is OUTSTANDING as Joe Devlin, I like his songs, his stories and limericks.

In addition I like
(1) Ransom for a Dead Man--Lee Grant's perfomance is not quite up to some of the others but the story is great and she does come across well as the seductive yet poisonous, absolutely despicable murderer.
(2) Make Me a Perfect Murder- Trish Van De Veer is great also, good story as well, this makes up for the fact that this is one of Peter Falk's weakest performanes.
(3) Negative Reaction-maybe the best plot of them all, plus great performance by Dick Van Dyke. Great comedy scenes as well.

YM, if you like the Conspirators, you should have a look at Colsy's site, another columbo forum at www.columbo.us.tt There I have posted the words to all the limericks from The Conspirators. On this site here, in the episode guide, there is an audio link in the Conspirators, but unfortunately it doesn't seem to work, well, it doesn't work for me at least.

Some of my faves (agree that there are so many to mention and much more difficult than least favourite) are How to dial a murder, playback, try to catch me, ashes to ashes, death hits the jackpot, swan song and the pilot (prescription murder) which i didnt really like at the beginning but now really enjoy.

God bless,

Mat

My top ten:

"Short Fuse," "Prescription: Murder," "Ransom For a Dead Man," "Rest in Peace, Mrs. Columbo," "Blueprint For Murder," "Dead Weight," "Columbo Goes to College," "Negative Reaction," The Bye Bye Sky High I.Q. Murder Case," "Agenda For Murder"

Also on my "A-List":

"Murder By the Book," "Death Lends a Hand," "Suitable For Framing," "Lady in Waiting," "Etude in Black," "The Most Crucial Game," "Requiem For a Falling Star," "A Stitch in Crime," "The Most Dangerous Match," "Candidate For Crime," "Double Exposure," "Publish or Perish," "Swan Song," "A Friend in Deed," "By Dawn's Early Light," "Playback," "Forgotten Lady," "A Matter of Honor," "Now You See Him," "How to Dial a Murder," "Columbo Cries Wolf," "Butterfly in Shades of Grey"

Here are my Top 10 favorites:
1. Identity Crisis
2. Candidate For Crime
3. Publish or Perish
4. A Friend In Deed
5. By Dawn's Early Light
6. The Conspirators
7. Troubled Waters
8. Playback
9. Etude In Black
10. A Case of Immunity

this week i would pick:

ransom for a dead man (always #1!)
a friend in deed
prescription murder
a deadly state of mind
etude in black
now you see him
death lends a hand
murder by the book
make me a perfect murder
identity crisis (even though i don't understand it!)

Lets try mine, In no particular order

How to Dial a Murder
Playback
Suitable for Framing
IQ
Butterfly
Now You See Him
Port
Agenda (Been a while though)
Publish or Perish
Hazardous to health

Reading this thread, I thought someone else was posting with my name, and thought it was a coincidence that another Paul also hadn't seen Any Old Storm, then I realised it actually was me, and the thread is nearly half a year old, I had completely forgotten about it. You certainly dug deep in the archives to revive this one Greenleaf

Paul you have cracked me up yet again!!!!!

I liked your choices Greenleaf!!