There have been posts a while back asking for Excel, but I feel a better case can be made for it. Microsoft Office is an amazing tool for almost any situation - high school and college students, professionals in careers, and for personal use.

In high school and college, Excel can be used to analyze data to an extreme degree with several functions that do a large number of calculations in a flash if you know how to. Some classes require you to use Excel or make a spreadsheet for data- while somewhat intuitive, there are various shortcuts and tricks that can cut the time it takes in half, as well as various functions you have to know are there to use. And the sooner you know how, the sooner you start saving time. Additionally, the amount of formatting and graphical tools it has can help make presentations and reports beautiful in record time. 

PowerPoint Presentations are a staple of high school and college, and the various tricks there are to speed up the process and avoid frustrating formatting errors could be an invaluable resource. 

For non science/engineering students, Word has several advantages if you know how to use it. The table of contents, bibliography, headings, controlling your formats, and a variety of other less-known features make it essential. Again, all of these won't make or break a course, but they will save a lot of time.

In a professional career, Excel is what I've used by far the most out of any program. As an added bonus, whenever there's an error in a formula or something breaks, less technologically savvy peers come to me for assistance, adding to my overall value in the workplace. It cuts down on the time it takes to do work and can greatly assist in data analysis to pull out information you need. 

There are also certification tests offered by Microsoft that are almost universally accepted and are always a solid mark in your favor on a resume. A test-prep for their intermediate and advanced certifications would be a plausible addition.

On a personal basis, Excel can be invaluable in budgeting and money management. I can and have: 

1. Tracked all expenditures and income I've had

2. Calculated how long it will take to pay off my student loans with various amounts of extra payments

3. Tracked if I'm overall gaining or losing money (spending more than I make or vice-versa)

4. Predict my net paycheck in advance based on hours worked, taking into account benefits and taxes

5. Created various graphs to show this in a clear manner and track metrics

There are also tons of budgeting, task based, etc. templates for anything imaginable if you don't feel like creating something from scratch.

There's a reason it's probably the most common software suite. It would be an extremely beneficial course to show some of it's more advanced functions.