I gave this assignment to my classes as part of a thematic unit on heroes and villains.
In groups, they present different elements of a coat of arms. Then they create their own coat of arms and write an explanation of the colors and symbols they used and how it represents who they are.
Included in this document is a diagram of a basic coat of arms to be labled by students.
The document is in MS Word so that it can be altered to fit individual teachers' needs.