National Grammar Day Is March 4

[2]  I’ll just pack up the picnic leftovers and give them to whomever can use them.

      Correction:  To whoever can use them. Think back to high-school English class, and the difference between a subject and an object. The entire clause “whoever can use them” is the object of the preposition “to,” and “whoever” is the subject of that clause.  Say it this way – “whom can use them” — and your ear will tell you it’s wrong.