#

Do not use this

Why?

1

Excel Add-in freeware like Morefunc or PimpMyExcel

You should have a license or at least the free source code for add-ins so that you can help yourself in case the provider vanishes. If not, it is a security threat, too

2

Array formulas

See my w-rule, please

3

Count unique list entries with SUMPRODUCT divided by COUNTIF

The runtime is suboptimal. Better use Charles Williams' COUNTU function which is much faster for more than 1,000 records. See my analysis here, please

4

Number format fraction

You cannot trust it because sometimes it is plainly wrong. Use my UDF NRN

5

Enable option Precision as Displayed from Calculate tab on the Options dialog (Tools menu)

A display format change in any input cell or intermediary cell can ruin the results

6

Enable option Iteration from Calculate tab on the Options dialog (Tools menu)

You will not see accidental circular references

7

1904 date system (to be able to present negative time = hours/minutes, for example)

Almost everybody is using the 1900 date system. If you switch between these systems you will need to remember the number 1462 by heart (to add or subtract it after CTRL + c with ALT + e, s, v and then d [add] or s [subtract])

8

Never ever test double precision numbers with = for equality. Use a test like
ABS(a - b) < 1E-13 instead

=(43.1-43.2)+1=0.9 does not result in TRUE as you might think, for example. See Microsoft's article on this topic here

9

Count or sum specified cells conditionally for all different elements of a list with SUMPRODUCT

SUMPRODUCT is powerful but unfortunately its also overstated and offered too often as a holy grail. See here, please

10

Worksheet function MOD(d,n) for
d >= n * 134217728

You will get a #NUM! error. See Microsoft's article on this topic here