David Eriksson performed this trick to great effect in his three ball routine at the Crawley Circus Festival 2002. It has the appearance of a member of the Shuffle family, but in reality is merely a Two in one hand pattern. All the best tricks are simple.
Start with all three balls & juggle two in one hand in a columns pattern. For the rest of this tutorial I'll call this hand the 'juggling hand'. Hold the third ball above the inside column (the one closest to the centre of your body), gripping it with only your thumb, fore & middle fingers. Keep juggling then when it comes to making a throw in the inside column, throw it up into the hand holding the third ball. Make the throw with more force than is necessary so that it would peak above your head if you did nothing about it. Catch this ball by using the little & ring fingers to press it against the ball that the hand is already holding. At the same time catch the ball in the outside column with the juggling hand.
Now simultaneously throw the ball held in the juggling hand straight up in the outside column as normal & at the same time Slam the ball from the inside column back down into the juggling hand. Continue juggling two in one hand.
All you are doing is catching a ball at its peak then sending it back down the way it came. Practise this catch & slam every now & then until comfortable. Then work up to performing the catch & slam on every throw of the inside ball. For best effect don't pause once all three balls are being held, one in the juggling hand & two in the other. The catch & throw rhythm of Eriksson's Shuffle should be the same as a normal two in one hand juggle.
Playing with this trick I have found loads of easy things you can do with it. Try switching sides either by carrying the slammed ball up on the other side after it is caught & the held ball down, or by slamming both balls held above the inside column at the same time & then catching the ball from the outside column in the non juggling hand. Also try catching & slamming every throw whilst juggling two in one hand with a rolling in pattern.
Another nice variation going back to catching & slamming on every second throw is to juggle a rolling in two in one hand pattern, after a slam, carry the held ball under the ball in the air. Then after throwing the slammed ball back up into the carrying hand, carry both balls over the top of the juggling hand to carry on the circling of the pattern.