The detective in the shabby raincoat, who smoked cigars. He was ace, wan't he?
The programmes always started by showing you a crime being committed, and the rest of the programme was showing how Columbo solved it.
There was no mystery at all to us as to who killed who, but it was addictive viewing watching Columbo slowly hone in on the criminal.
In a few earlier episodes, he also took along his droopy eared dog. I don't think he was much help though, unless you count gathering slavvery dog-drool as evidence.
Columbo was, and to this day still is, played by Peter Falk.
My favourite joke was when his assistant asked if he needed any help looking for clues, and Columbo replied, "Sure, why not, 3 eyes are better than 1."