"Hello. Who's this?"
BZZTTT!!! Wrong question. This sort of telephone initial inquisition irritates me to no end.
I come by this pet peeve honestly. Any guy who called to speak to me or to one of my sisters and who didn't something like "Hello, Mrs.___/Ma'am. This is ___. May I speak to Juliette/T./S.?" when my mom picked up the phone was guaranteed to be on her feces list until later redeemed--if at all.
The telephone rule specifies that one should put forth the old skool niceties and, after that, get down to the business at hand. Then--and only then--is a caller deserving of the reciprocal niceties and, subsequently, deserving to speak to the individual desired. There are no exceptions--business or personal.
Some years ago, my stance on telephone etiquette served to give up a bit of amusement. An errant SO of a man friend of mine decided to ring me up.
"Hello, who are you?"
Me: "Um, who would you like to speak to?"
"I want to speak to you. What's your name." Arrogantly asked.
She never got my name and the upshot is that she wanted to know whether I was doing the deed with her boyfriend. The answer was truthfully 'no,' but I had fun before I gave up the answer--simply because of her violation of my telephone rule.
Even those who dial the wrong number must follow the rule.
As an aside from this personal pet peeve, I found out a number of years ago that there are some people who get a kick out of harassing senior citizens on the phone. A person who had originally dialed the wrong number to my great-aunt's exchange decided to harass her for a few weeks after the first call. Fortunately, this creature decided to call on an occasion when I was present and my aunt put me on the phone. After the caller and I came to a "mutual understanding," she decided that it was best to not call my aunt anymore.