5 There's only a little / a few pie left.

Pie can be countable (e.g., slices of pie) or uncountable (e.g., the substance of pie). Given the context 'only a little/a few', it implies a small quantity. 'A few' is used for countable nouns, and 'a little' for uncountable nouns. If referring to slices, 'a few' would be appropriate. If referring to the pie itself as a mass, 'a little' would be appropriate. However, 'pie' as a whole item is countable. Thus, 'a few' is the better choice.