Well, well well, aren't we all in love with the API.
I personally am rubbish at the API, so my favourite
functions are standard VB ones.

My favourite functions then, as no one else has mentioned
them.

InStr The basis for all string manipulation.
Mid$ Goes with InStr, you can forget about Left$()
and Right$(), you dont need them

Get #1, , variable Wonderful for fast file access.
You can also control the file in manageable chunks. If you
get the chunk sizes right, you can manipulate files much
quicker than with the FSO, and slightly faster than the
Input functions.
Put #1, , variable Obviously paired with Get