This came up recently with Monk start Tony Shalhoub being an excellent candidate, though hard to imagine him making transition from neat and OCD to rumpled and sloppy.
Don't know how well this choice will go over, but i think Tim Roth could pull it off. Lie To Me was one of my favorite shows when it was on and he can pull off some comedy, if anybody has ever seen Four Rooms.
A wise man with a vision once thought long and hard about this very matter and then said: "Johnny Depp. He's inventive, eccentric, and downright weird, and he is, like Peter Falk, a clever, resourceful and "thinking" actor. I can see him throwing all of his imagination into both reenacting and reinventing the character."
The wise man continued, "The result would certainly be controversial, especially among hardcore Columbo fans, but it would also surely be thought-provoking. If he failed, he would go down in a blaze of creativity."
I myself would love to see what Johnny Depp would do with Columbo as a character and "Columbo" as a project.
But who was that wise man who said all that? Trying to remember. Hmm, yes... Who was it that Ted that?