1) Richelle Mead - I actually haven't read any of her adult stuff, simply because I haven't gotten my hands on any of it. But I pretty much worship her, I have a whole drawer in my entertainment center dedicated to her YA books.
2) Lauren Oliver - I haven't read her MG stuff yet. But lemme jus say, if I could pick one author to write like, it would be Lauren Oliver. She is AMAZING.
3) Sarah Dessen - Nuff said.
4) Cassandra Clare - Though I would love her to branch out of the Shadowhunter world, I do adore everything she has ever written. Girl has a way with characters and plots.
5) Jenny Han - ALL DA FEELZ!
6) Katie McGarry - I can't even use words to describe what Katie McGarry does to me.
7) John Green - I've only actually read 1 of his novels, but, uh, WIN.
Those are the only authors I know of whose writing I have utter faith in. What about you?