Prompted by a post over at Nathan Bransford (yes, I had to double check the spelling!)
I too don't give a rat's ass what you call me in a query. I know other agents DO get hot under the collar about salutations so it's probably one of the things you want to get right.
What's universally wrong is Agent Snookums.
This is a usage that has crept into the lexicon and I'd like to take aim with my blunderbuss and wipe it out post haste.
Agent is my job. It's not my title. My title is Queen of the Known Universe and Don't You Forget it Bubbelah, but you can just call me Snookums.
Dear Agent Reid, Dear Agent Janet, and worst Dear Agent, are wrong. As in not right.
Dear Miss Reid, Dear Ms. Reid, Dear Mr Reid, I don't really care. Dear Mrs Reid creeps me out but I can live with it.
None of these kinds of mistakes mean I stop reading your query. But, if you like to get things right, this is one of the places to pay attention.