What Excel skills are most valuable for finance and accounting?

It depends on what kind of career you are planning to opt for after graduating from college. Having stated that some of the most general things one must know in Excel who is finance and accounting majors are:

General formatting- Coded inputs to be in blue, calculated fields in black assumptions in red/green. One would prefer keeping the entire background white and shading assumption cells with grey etc.

Pivot tables, We hear this a lot in job interviews in which students are given quick Excel project to check their chops. Pivot tables are a big part of that. Stuff like a new worksheet with each new month's data in it. This could make workbooks look huge. It is recommended to use pivot tables for this too.

=sumproduct() is a must-learn and =subtotal()  is a great function that helps your Excel spreadsheet look like something somebody would do on paper.

Naming cells and ranges. If you could learn this, then you separate yourself from a novice from a person who has stepped up a grade.

Custom formatting. Here, usually, the users would like to be able to format numbers, so the digits stack on top of one another is going down a column, especially if they are trying to centre them and they have an odd number of digits.

Learning to use templates for shared files. Charting can be hyperactive in Excel. It is a huge time consuming and is advised to learn it in full.

Most importantly, financial formulas can be of great help for you to learn. Majority of students avoid learning the underlying finance. But, it is advised to make sure you learn this too. It will be a saviour on a rainy day.

Hope this helps