Prelude
I have found countless ways to get the value of an sObjectField using a variable. E.g.,
What I've Tried
a.n = 'New Account Name'; // Results in "Variable does not exist: n" error.
Use Case
In a test data factory class I was wanting to iterate a map that has field names and values (where the field names could be different every time) and then create an object with those field names and values. If I can't use a variable to set a field name, I'm going to have to go through and check every possible field name.