You do not need to use macros each and every time when you like to solve a problem. Solutions based on worksheet functions can be fast, simple and easy to use.
Calculate annuities of mortality tables
Simple charts can be created via characters in cells: cell based charts
Create a list of unique identifiers and their frequency.
Count Trailing Zeros
Use COUNTIF to create a list of unique identifiers
Fill gaps in a table of numbers with linear interpolation
Show cell formulas with GET.CELL
Make rounded percentages sum up to exactly 100% with the Largest Remainder approach
Lock a formula so that it does not get adjusted to added or deleted cells.
Some maybe controversial material on "obsolete" worksheet functions.
Show numbers as ordinals such as 1st, 2nd, 3rd, etc.
Test for overlapping ranges
Calculate N significant digits of a number
Sorting data automatically
Test with MEDIAN whether a value is between two other ones
Count or sum conditionally with potentially more than one condition with SUMPRODUCT
A vacation planning tool can help you to organize your teams' holidays.
However, there is a German web site www.excelformeln.de which claims you have landed on the ultimate Excel formula page. Not for beginners, they start where the online help ends. Now, my thesis is that this web site is presenting some 'toxic waste' worksheet functions.