The Tam o' Shanter is a HatItem that is obtained by killing MacTusk. It restores 6.7 Sanity per minute while worn, making it the most civilized of all hats, and as such, the best for restoring Sanity. It's enough to cancel out the Sanity drop of heavy Rain or the Night, even when playing as Wolfgang.
A Tam o' Shanter, often abbreviated T.O.S. or Tam, is a nineteenth-century Scottish traditional bonnet worn by men.
Because of MacTusk's death animation, when the Shanter drops, the player will actually see two of them drop from the walrus. One is the item that the player can pick up, while the other is part of the animation and will disappear with MacTusk.
The Tam o' Shanter is the most dapper piece of clothing in Don't Starve.
In addition to having the highest sanity gain and being a tier 2 insulation item, it lasts the longest out of every clothing item in the base game, with a maximum lifetime of 25 days.