top banana

1. The main comic in a burlesque show.
2. The head person, as of a group or project.

[So called from the presentation of a banana to the comedian who has the punch line in a three-man burlesque routine.]

The noun has 2 meanings:

Meaning #1: the leading comedian in a burlesque show

Meaning #2: the most important person in a group or undertaking
  Synonyms: kingpin, bigwig