If Wikipedia knows it, it’s official; Rubber Duck Debugging is a new tool in my developer toolset!
I first heard about this technique here: http://www.codinghorror.com/blog/2012/03/rubber-duck-problem-solving.html.
An extract from the original story:
Bob pointed into a corner of the office. "Over there," he said, "is a duck. I want you to ask that duck your question."
I looked at the duck. It was, in fact, stuffed, and very dead. Even if it had not been dead, it probably would not have been a good source of design information. I looked at Bob. Bob was dead serious. He was also my superior, and I wanted to keep my job.
I awkwardly went to stand next to the duck and bent my head, as if in prayer, to commune with this duck. "What," Bob demanded, "are you doing?"
"I'm asking my question of the duck," I said.
One of Bob's superintendants was in his office. He was grinning like a bastard around his toothpick. "Andy," he said, "I don't want you to pray to the duck. I want you to ask the duck your question."
I licked my lips. "Out loud?" I said.
"Out loud," Bob said firmly.
I cleared my throat. "Duck," I began.
"Its name is Bob Junior," Bob's superintendant supplied. I shot him a dirty look.
"Duck," I continued, "I want to know, when you use a clevis hanger, what keeps the sprinkler pipe from jumping out of the clevis when the head discharges, causing the pipe to..."
In the middle of asking the duck my question, the answer hit me. The clevis hanger is suspended from the structure above by a length of all-thread rod. If the pipe-fitter cuts the all-thread rod such that it butts up against the top of the pipe, it essentially will hold the pipe in the hanger and keep it from bucking.
I turned to look at Bob. Bob was nodding. "You know, don't you," he said.
"You run the all-thread rod to the top of the pipe," I said.
"That's right," said Bob. "Next time you have a question, I want you to come in here and ask the duck, not me. Ask it out loud. If you still don't know the answer, then you can ask me."
"Okay," I said, and got back to work.
I do think it’s useful for the same reason I like buddy reviews and teaching concepts to others. By explaining a problem to someone else, you get new insights, learn new stuff and discover things you forgot.
Next time you see me talking to a rubber duck, don’t think I’m crazy. I’m just debugging my code… 
