A unique screw cap is the trigger sprayer, found on many glass cleaners and other household products.  This screw cap basically includes a straw and sprayer that allows a product mist to be shot from the closure.  The trigger sprayer can easily be tightened down using a spindle capping machine, but presents some problems for the chuck cappers.  The capping head on a chuck capper normally descends over the entire cap, and then applies torque to create the seal.  The large trigger and spray head make this impossible, making the spindle capper the logical choice for these types of closures. The spindle capper, rather than descending over the cap, uses spinning discs and contacts the edge of the cap to apply the torque.  

While there are other variations of the screw cap, those listed above currently reign as the most popular.  Similarly, though the screw cap seems to be the closure of choice in today's packaging world, other closures do exist.