Collarbone or Clavicle
The clavicle -- or collarbone -- rests between the upper ribcage and the scapula (shoulder blade) and is an important bone, as it attaches the arm to the body. It's prominent position -- coupled with its long, slender shape -- means it is one of the most common bones to break, especially when it comes to the active, rock-'em-sock-'em lives of kids.
Babies can even suffer clavicle fractures during passage through the birth canal, but fortunately the bones of children and infants heal extremely quickly.
Fractured clavicles also commonly occur in sports, especially if it's a backyard pick-up game where players aren't wearing any type of body-protection or padding. Car accidents also frequently lead to clavicle fractures, as a result of impact with either the seatbelt, steering wheel or from bracing against the dashboard with extended arms.
When the clavicle fractures, it usually does so right in its middle. You'll know you broke yours if your arm is suddenly rendered useless, while a bump develops on the clavicle. No surgery is needed if it's a non-displaced fracture and both sides of the clavicle are still lined up properly; an arm sling usually suffices. For displaced fractures, however, surgical plates or screws may be required for the bones to heal correctly.
Next: a bone we all-too-often place in harm's way, as a means of keeping us out of it.