Scarecrow

Scarecrow is an creature type used for cards depicting vaguely humanoid objects dressed in old clothes.

With the exception of Straw Soldiers all Scarecrows are artifact creatures.

History
The first creature to bear the type Scarecrow was the original Scarecrow from The Dark, though it only gained the subtype first in the Grand Creature Type Update, together with Straw Soldiers from Portal Three Kingdoms. Shadowmoor block added 23 Scarecrows at once. Mechanically they often deal with colors and -1/-1 counters.

R&D had considered Scarecrow tribal for artifacts in Innistrad, but decided it didn't fit cleanly into the ally-colored “monster/victim” tribal. One card remained; One-Eyed Scarecrow discourages flying creatures just like the original Scarecrow and the intended purpose of real life Scarecrows.

Shadowmoor
Scarecrows originally were just simple objects to keep birds off of the crops. The scarecrows of Shadowmoor were magically enhanced by kithkin cobblesmiths to help them with farming. Over time, some of them got lost or outlived their creators and took on a life of their own. Those scarecrows are led by the Reaper King.

Trivia

 * Straw Soldiers is the only non artifact creature Scarecrow.
 * Reaper King is the only multicolored artifact Scarecrow.