Tryhard

A person who tries too hard to be liked by acting in an insincere manner inconsistent with their true personality. Usually manifested by the person attempting to take on the persona of a funny or amusing or "life of the party" personality, and failing miserably.

At the conference, Cynthia continually threw out unfunny quips, laughed just a little too loud, and overly-complimented others, bringing accusations of "tryhard" from her fellow attendees.