What are the coming-of-age rituals commonly practiced in your country or region thereof?
In the United States, the most dramatic coming-of-age ritual for boys and girls alike has been the acquisition of a driver's license. Most states allow individuals to drive independently (without parents) at the age of 16, though many have enacted various restrictions (no late night driving, on the # of teenagers in the car) until the age of 18. This is called "graduated licensing".
A common 16th birthday present in families who can afford it is a car.
This allows the individual a tremendous amount of freedom, as most people in the U.S. live in car-centered communities.
Another coming-of-age ritual in Minnesota and the Upper Midwest, for males mostly, is the completion of gun safety courses, allowing the young man (12 years and up) to shoot a deer (which will usually be processed for food), and more importantly, to spend bonding time with the older generations of family males in the deer stand and hunting shack.
Deer Hunt 2010 7 by
elviskennedy, on Flickr
A similar thing is the completion of a snowmobile safety course (8 hours in Minnesota) and the acquisition of a snowmobile permit (available, I believe, at the same age or younger than a gun safety permit), which enables the boy (or girl) to ride on the groomed snowmobile trail network and socialize with the older relatives and friends of the family.
Some, especially from the South, have a "Sweet 16" for girls, complete with a debutante ball in some families marking their debut into society:
Ashley's Sweet 16 Party by
Lee Gonzalez Photography, on Flickr
An interesting current with some devout Christian families across the country is an event known as a "purity ball" or "father-daughter ball", in which girls pledge to remain chaste until marriage and fathers pledge to protect them. This definitely goes against the mainstream culture. Girls dress in gowns and the fathers in equivalent formal wear.
And of course we have quinceañeras and equivalent celebrations within the respective immigrant communities.