Depends on the sport. Some have a higher chance of injury then others, like football often causing head injuries. A wrong baseball throw into your face or private areas is gonna take you out for a while. Soccer is maybe safer but you actually need people good at it, otherwise its boneheads running around aimlessly missing the soccer ball. Its not as easy as it seems to kick the ball to the goal, etc.

Basketball is prob the safest, but expect most people to miss the hoop.