A recurring issue we have on the marketing side is that an applicable link/other resource that can stretch across all tasks is added to each task in the list individually. I think it would be of great benefit to be able to choose certain custom fields on a per-list basis that have the same information across all tasks, centrally located in the List, Task, and Subtask views respectively. In this way, one of these overarching custom fields can be filled out on one task (say by a designer that's linking to an image) but be filled out on another task (say the IT person's task to update the image on a site).