Have you ever thought about the moments that have shaped you as a writer? They might be personal moments, or they might be things you've read that have stuck with you. I'm re-reading Pratchett's Pyramids at the moment, and there's one line there that I always remember, about them being such a small kingdom that the best plague they could manage was the plague of Frog (but it was quite a big one, and got into the air ducts and kept everyone awake for weeks).
There's just something about that knack for taking an ordinary idea, such as 'Egypt had famous plagues' and twisting it on its head like that. Then adding another layer. Right there, as a throwaway line, there's something so well constructed and memorable. I think I remember this joke because it's one of the first ones where I really saw the craft at work.
There were other big moments for me in terms of what I read. Tom Holt work, and particularly his portable door series, was in many ways more important than Pratchett for me, because it showed me that this idea of writing funny stuff wasn't confined to one person. It also had that level of normality in amongst the odd stuff.
Then there was reading Neverwhere. Gaiman's American Gods was impressive, and a brilliant piece of fiction, but it was Neverwhere that caught me more. Perhaps it was the English setting. Perhaps it was just the level of oddity there. Whatever it was, it left me with the feeling that it should be possible to write very strange things and still have them work. Oh, and Grave from Court of Dreams originally started out as two hunters, along the lines of Croup and Vandemar.
Those are the moments that come to me off the top of my head, but I think the beautiful thing is that almost everything influences everyone. Even the things you don't like. Perhaps especially them in some ways. We take the world and we respond to different bits of it, fitting together our own little views of how it works. Maybe that's what it's about, writing.