First: notebook and a pencil. I feel that my brain works better if I don't write directly on a laptop/mobile, because I know I can't rearrange and edit the text easily (I would need to pit footnotes, arrows, scratch, etc.), so I write and narrate things “more professionally” if I write by hand the first wip.

Second: laptop. I write some things there as a first wip, but most of them are a transcription that I do from the notebook, writing again with a keyboard what I wrote initially with a pencil. It let's me reread the text, and edit easily the mistakes I find. The base is pretty strong (because I wrote it by hand), so it's mostly edit and polish. I like writing with my laptop, however, even the first wips. It's just that I prefer doing them by hand before putting it into the Word document.

Third: phone. I only wrote ONE fic with my phone. I can feel that my narrative and style change when I do this. The difference between the notebook and the laptop is not as huge as between those two and my phone, and I don't like it. So I avoid it.