One that the post-Schism West, sadly, has by and large forgotten: The Feast of the Baptism of the Lord Jesus Christ our God (celebrated on 6 Jan.). The ramifications of this event for man and the creation, however, are anything but small and forgettable. They will resound for all eternity, as we see in one of the hymns for the Forefeast of Theophany:
Prepare, O Zebulon, / and adorn yourself, O Naphtali; / river Jordan, cease flowing / and receive with joy the Master coming to be baptized. / Adam, rejoice with our First Mother / and do not hide yourself as you did of old in Paradise; / for having seen you naked, / He has appeared to clothe you with the first garment. / Christ has appeared to renew all creation.
Read more about this Feast here:
--This holy icon of the Baptism of the Lord is from the page linked just above.
Holy Ælfred the Great, King of England, South Patron, pray for us sinners at the Souð, unworthy though we are!
Anathema to the Union!