Note: Please take the material offered here as an intellectual challenge. You should be aware of the fact that Excel © is a historically grown application. This means it is providing a historically grown (better: kept) functionality (read: behaviour). Of course it is good to know all functions because they are mostly the fastest solution (in terms of calculation speed) if you only need their limited functionality. But the functions shown here are quite limited. In many cases I needed a more flexible or enhanced functionality. Which I happened to find with other functions or approaches. So this is meant by “obsolete”.
I think obsolete functions are:
Countif  Better use Sumproduct Rank  Better use Countif (or Sumproduct, if you like :) Sumif  Better use Sumproduct
In my opinion semiobsolete functions are:
Offset  Better use Index Sumproduct  Better use pivot tables or my UDF's shown here
Some fun function replacements:
LEFT(A1,n) = MID(A1,1,n) RIGHT(A1,n) = MID(A1,LEN(A1)n+1) MID(A1,m,n) = RIGHT(LEFT(A1,m+n1),n)
