1. The thing I used this for wad to decode and encode BASE64 strings. (-decode and -encode command switches) .It has two annoying features here - for decode and encode it needs
-----END CERTIFICATE----- and -----BEGIN CERTIFICATE----- at begining and at the of base64 file.And it prints decoded file in lines with max length of 64 symbols.
So here are two very very very simple scripts that use certutil to decode and encode base64 string (and dealing with begin and end tags) (there are no checks for file existence and if the parameters are correct - I rely on certutil error messages):

decode:

@echo off
setlocal
for /f "delims== tokens=1" %%A in ('type %1') do (
	set encoded=%%A
)
rem two additional lines are needed by certutil
echo -----BEGIN CERTIFICATE-----> %2.tmp
echo %encoded%>>%2.tmp
echo -----END CERTIFICATE----->> %2.tmp


certutil /decode %2.tmp %2
del /S /Q %2.tmp
endlocal

encode:

@echo off
setlocal
certutil /encode %1 %1.encoded
rem create an empty file
break > %2

setlocal ENABLEDELAYEDEXPANSION
(
	for /f "eol=-" %%A in (' type %1.encoded ') do (
		rem this not works - left an empty spaxes after each line from typed file
		rem null< (set /p #=%%A) >>%1.encoded
		
		set result=!result!%%A
	)
)
endlocal & set result=%result%
echo %result%>> %2%
del /S /Q
endlocal

The bad thing is that the base64 strings are stored in a variable and there's a limitations for it's size.But for a small strings it wokrs.

2. Much more interesting.In the help it shows that there's an -decodehex switch.And I was surprised to find that there's also an undocumentes switch -encodehex (strange - decodehex looks more dangerous , because it can be used to produce binaries). Here's an example structure of encoded file:

(just as every hex editor)
This was my attempt to create file that set LF and CR to variables smile - and I still don't know why it was unsuccessful it prints "§↕" (any help here will be welcomed - I don't know what goes wrong).
EDIT: I've set DEC codes instead HEX .Anyway still not works.
In fact the data that is behind the hexes is not necessary - it's only for visualisation .
To decode the sample just use this (if this above is saved in sample.hex) :

certutil -decodehex sample.hex not.working.bat

Any way it works for creation of the famous beep.bat :

0000 65 63 68 6f 20 07
this pattern can be used for creation of bat that echoes a random symbols by hex.Just edit the last character.
and this is a pattern for setting a symbol by hex to %#% variable (just edit the last character):
0000 73 65 74 20 78 3d 15 0d
Anyway there are few more things that I want to try with this smile