Cheat: Turkey Assassin
Assassin's Creed III is as large as any open world game, and with that, possibilities for secret are pretty much everywhere.
One of the more interesting ones involves a turkey. To get a turkey sidekick, progress to Sequence 6 or later. Return to the Davenport Homestead and as you face the front door, walk around to the right side of the manor. Now hide around the corner at the back. Whistle to get the attention of a turkey. Go to it and press Up, Up, Down, Down, Left, Right, Left, Right, B, and A. The turkey will now sport the Assassin's hood, sticking to Connor's side.
Best. Sidekick. Ever.