What is a good word for “best example”?

Solution 1:

I would suggest epitome.

(the epitome of) a person or thing that is a perfect example of a particular quality or type: she looked the epitome of elegance and good taste

Oxford Dictionaries Online

Solution 2:

How about Exemplar 1 (if you need a noun)

a person or thing serving as a typical example or appropriate model: the place is an exemplar of multicultural Britain

Or Exemplary 2 if adjective

serving as a desirable model; very good: exemplary behaviour

Solution 3:

Dictionary.com defines paragon as

a model or pattern of excellence or of a particular excellence: a paragon of virtue.

EDIT: Current usage of paragon in the context of films:

Casablanca:

...leading as it does to the most famous movie scene of all time, is held up as a paragon for subsequent generations of aspiring screenwriters...

Black Swan: (blog title) "Dramatic Film Paragon."

Solution 4:

Besides epitome, you might also want to consider,

• Ultimate: 2 being the best or most extreme example of its kind: the ultimate accolade
• Quintessence: 1 the most perfect or typical example of a quality or class: he was the quintessence of political professionalism