The funniest lines ever are those at the end of "Death lends a hand", when Columbo tells Ray Milland that as a matter of fact his wife did have both contact lenses hinting at setting up a trap for Brimmer and (maybe?) at putting a "fake" lens in Brimmers' car trunk.
Then Columbo tells Milland about him when he was a boy in a gang and used to put cars out of commission sticking a potato in the exhaust pipes (referring to what he just did with Brimmer's car); and, finally, Columbo says he feels he entered the police to make up for all those bad actions.

All that hinting at lies, traps, actions that Columbo has (or may have) done is fantastic!

This is, by the way, one of my favorite episodes.