Evernote (free) might not feel like an ideal to-do list app, but it can definitely work as one. You can create different notebooks with lists and insert links and files at will. You can tag and search your notes, use the camera to add more information or to scan something, and, of course, share any note with someone. There are two pro options: Evernote Plus ($4 monthly, $35 annually) and Evernote Premium ($8 monthly, $70 annually). The Plus version comes with the ability to see your notes offline, and the Premium one lets you search Word Docs, write on PDFs, and more.
Available for iOS and Android