I'd pick Etude in Black (the network premiere in '72 was the first Columbo I ever watched), By Dawn's Early Light (the most cinematic episode, and, c'mon, McGoohan?), and, though there are so many greats from which to choose, Murder Under Glass, because I love the humor, the food, and the fantastic barb-tongued exchange in the finale.

I was watching this triple bill and thinking the same thing. Great triple.

Boy, that makes for a tough call, but impulsively, I'd have to say "A Friend In Deed," "Candidate For Crime," and "Troubled Waters." I could watch those eps back to back forever. And by the way, I couldn't stand Jordan and Shatner in their respective Columbo roles.

Identity Crisis > Forgotten Lady > Now You See Him

Murder by the book,Publish or Perish and Now you see him are an obvious choice due to Jack Cassidy being the guest villain in each of them and being the best one. All three of these are a joy to watch.

But failing that i guess i'd go for

Double exposure - best Culp episode
A Friend in deed - Darker than most episodes and very strong ending
Make Me A Perfect Murder - Trish Van Devere is my favourite female killer

or
Suitable For Framing
A Stitch in Crime
Negative Reaction

ugh its hard to pick just one set of three!!