The Brine championship replica mini balls ($10) are available in the triumph or phantom styles.  Constructed of a soft polyurethane, they are somewhat safe in the house and fun play balls.

The Brine minis are very light weigh and best kept indoors or on grass.  The butyl bladder is soft enough for this level of ball and retains air well.  These balls are available in two styles.  The blue and white hurricane graphic ball is based on the Triumph premium match ball that won our 2007 Ball of the Year.  The black and white phantom is based on the perennial NCAA official ball.

Mini balls are more for advertising and fun than serious training.  That doesn't make them any less important to have in the bag.  There is a reason that they are also called skills balls.  Practicing ball control drills and tricks with different sized balls forces the player to feel the ball and be aware of the field conditions.  We don't think that everyone needs to go out and by a mini for training, but they do make nice presents and team awards.