Hey, good lookin’ !
To my new BFF.
Yo!
are all probably bad ideas as well
Just stick with “Dear Sir or Madam”.
While it might seem odd to you, the person receiving the letter doesn’t even really notice - they get tons of letters and skip over salutations in a mega-second. For them, this is just blah, blah…but “normal” blah, blah.
Trying to be clever will simply put you in the “unprofessional” stack of applicants.
I used to hire lots of people and would get stacks of letters - any letter that was “cute and quirky” usually ended up at the bottom of my stack and I would not bother calling them in for an interview; pink paper, smiley faces, weird fonts, bright color fonts - childish gimmicks of any kind - didn’t exactly bode well for potential professional employee of the month.
So “What up bitch?” is out then? 
I’m not sure why you’d need an alternative to “Dear Sir or Madam.” It’s the standard business style for writing to an unknown person. Why would you want a notch less formal? Less formal for a job application? That’s pretty much as formal as it gets in the business world.
In academia when the name of the chair of the search committee isn’t given I address it to “Dear Search Committee”.
Personally I think “Hello” sounds better than “Greetings”.
Though I always liked the opening I’ve read in some history books by kings who didn’t have the time to figure which honorific worked:
“To Ultraman 100 of the Dope, Whatever greeting is due unto your station. We’ve got Saxons out the ass up here so get an army up here pronto.”
I usually go with “Yo, Homie!”
(Seriously, everyone I know - including me - uses “Dear Sir or Madam:”)
Use an augmented reality tag in place of the greeting and have it link to something like Stephen Hawking’s voice synth.
I just put “To whom it may concern” - generic is best, I think.
There’s nothing generic about using “Greetings;” as a salutation in a business letter. Especially with that semicolon; people are liable to think you don’t know how to write.
I think:
“Good evening, Ladies and Germs. How are ya, how are ya, how are ya? But seriously…”
is a good start. And then sign off with a flourish:
“I wish you and your family the most effusive of salutations,
I remain,
Your most Humble Servant,
Captain Sir Peter Uxbridge, Esq.”
I always use “Dear Hiring Manager” in that situation.
You are correct. Thanks for making me look again at this and I have now altered my salutation and punctuation.
deleded
I use ‘Sieg Heil!’ But, that’s only for casual and romantic correspondence.
When I’m looking for a job, I go with 'Hello," or “To the Human Resources Department,”
Best wishes,
hh
I use re: position/job name. I have seen that before and it makes sense to me.