I fell to thinking about this after reading Jonathan Strahan's blog. Not which writers exactly, but the "unanswerableness" of the question.
If you look at my blog profile, you will see that I didn't answer those questions about "what is your favorite movie/book/music..." etc. I find them as senseless as Jonathan does. I like all types and how do you compare a 1930's b & w classic film to, say Crash? And even when I admit to having favorite authors, stacks of them, how can you compare Terry Pratchett and Guy Gavriel Kay and Ian Rankin?
And so, which authors have influenced me? ...Well, I can tell you one author who had a definite impact at a very early age. She wrote gripping stuff, unputdownable, in which I immersed myself entirely. One of her books was probably my first lesson on using tension to keep the reader's focus.
Trouble is, I can't remember her name, and I am not sure which book it was - although I can tell you the name of the series. They were all about a girl called Milly Molly Mandy, and I was just five.
And why on earth would I be able to remember its impact? Well, I was on my way to school back in - well, a long time ago. I paid tuppence for a two mile ride on the Perth/Armidale bus down Albany Highway - which was a very rural road at that time. I was reading - and went past the stop near the school because I was so engrossed. The bus disgorged half a dozen other children, but not me. When I did realise what had happened some time later (on raising my head from the book), I wailed - loud and long. The bus conductress - I even remember her name, Inez - told me not to worry, I could go on to the depot and then the bus was going to turn around and come back again. She would put me off at the correct stop. I was still traumatised. And humiliated too - it was all over the school and the community to the extent that my parents knew about it by the time I arrived home from school that day.
Yep, there was a book that influenced me. Taught me never to get too engrossed in reading while riding public transport. My first lesson about the power of the written word.