negative reaction would be a goodie...lots of humor in that one.
forgotten lady...is fantastic...although the ending is not the normal columbo ending.

Perhaps "A stitch in the crime" would be a good to watch, because the ending is very interesting, a murderer tries to trap Columbo.

Next one might be also "Dagger of the mind", because Columbo "falsifies" a proof to proove the murder.

And perhaps..."How to dial a murder" when Columbo shows a murderer exactly the same how the murder happened.

I just gave three examples of 3 different perspectives, there are many more interesting.Enjoy.

um........and there's always etude in black

I would recommend "Negative Reaction." A lot of good clues, good tension between Columbo and the murderer, and that unforgettable cemetery scene which helps to define Columbo's character.

Agreed..."Negative Reaction". Has it all, great chemistry, just enough humor (not too much),
Columbo is
"modest and mildly eccentric" to the right
degree, a really clever set-up by Galesko making
the case seem uncrackable,
great acting by the victim (who often ends
up as a cipher in the different stories)
Antoinette Bower ("what is this Paul, some
newly found masculinity?") and great directing
and camera work. A "10"!