The portrayal of Dogberry by Michael Keaton in Branagh's version of this play immediately comes to mind. Keaton played it perfectly: Dogberry is lacking in manners, refinement, vocabulary--anything remotely resembling class and intelligence. He means well and is an honest person, but he lacks the insight and charm to perform his job and to communicate with others. For example, he becomes outraged when one of Don John's men calls him (aptly enough) an ass. He then insists that the sexton record the comment, thereby perpetuating the impression of him as an ass. He does bring the evil-doers to justice but he does so in such a manner that everyone laughs at him. He is rude and crude.
Dogberry — Illiterate master constable, whose love of high-faluting words is only matched by his misuse of them, exposes the slanderous deception, thereby saving Hero.