St. Michael is often a fan favorite, especially as the patron Saint of soldiers, police officers, and EMTs. He can be found in the Bible in Revelation 12:7-9 and Daniel 10 & 12. His name means "Who is like God," appropriate since St. Michael drove the prideful Satan out of Heaven.
I created this block print image of St. Michael especially with one of my nephews in mind- Michael has long been his favorite Saint. Click below for printables you can use yourself, including some prayer cards:
If you are looking for a lesson to teach for their feast day, you might like this Lectio Divina style Bible Study on the Archangels, which also includes some matching bulletin board printables: