Was watching "Old Fashioned Murder" (highly underrated I'm beginning to think...) and the hairdresser Darryl drops these lines at Columbo.

First, when Columbo approaches him, Darryl says, "A challenged but I'll do my best. Sit, sit."
When Columbo says he just wants to ask him a few questions, Darryl says, "Oh, don't sue. Just wear a hat and never let him cut it again."

Columbo asks if it's really that bad, and gets this response from Darryl, "Mmmm hmmm, yes. Yes"

Have to add that nothing is funnier than seeing Columbo with his new hairdo and manicured nails, looking at a $25 tab, having only $5 in his wallet and then hitting up Sgt. Miller for $20 AND whatever tip that MILLER felt comfortable leaving.

I want to add that if you're looking for the scripts of every Columbo episode, this site has them: https://www.springfieldspringfield.co.uk/episode_scripts.php?tv-show=columbo-1971

It's been very helpful and interesting going through these. It's not like a screenplay, so you can't see who made the comment, but if you've seen them as much as I have, it won't really matter.

It isn't precisely an insult, but there's Ward Fowler'a line that goes something like "Look, let's stop pretending that I'm brilliant and you're stupid."

That one line covers so much about Columbo's behavior towards a killer.

Ken Franklin to Columbo: "I love to see a man raise with no cards in his hand."

Just because he's played by Ray Milland (who was so great at playing smug characters), Jarvis Goodland has some catchy ones. Even though it isn't said to Columbo himself, there's "That Neanderthal lieutenant."
It might not be that original, but Milland makes the most of it.