Blowing the ram's horn on the High Holidays.
A shofar is a ram's horn that is blown like a trumpet during Rosh Hashanah services, and at the end of Yom Kippur. The four sounds of the shofar--tekiah, shevarim, teruah, and tekiah gedolah--remind many people of a crying voice. Hearing the shofar's call is a reminder for us to look inward and repent for the sins of the past year.
The shofar is created by hollowing out a ram's horn, shaping it, and polishing it. It's a tricky(and occasionally smelly) feat that doesn't always end up the way you think it will. But it's a rewarding task, nonetheless.
The shofar is evocative of the Torah portion that we read on Rosh Hashanah, the story of the binding of Isaac. It calls to mind the image of the ram stuck in the bush that Abraham ultimately sacrificed instead of his son--reflecting our own sometimes difficult parent-child relationship with God.