In this modern game of topspin, many players battle to see who can get more topspin on the ball, with more speed and more consistency. After all, isn't that what tends to win games? Yet you might want to consider whether you want to join in this escalating topspin battle every single point. Why not throw an occasional changeup at them - a "dummy loop" - and watch them mess up? Go for less spin, and mess up your opponent's consistency!
A dummy loop is a loop that looks like it has a lot of topspin, but is not very spinny. You execute the shot almost like any other loop, except you start with your wrist cocked up, so there's no natural wrist snap, so little whipping action to add to the topspin. By using a full motion, and exaggerating the rest of the stroke (especially the follow-through), it looks like you've done a normal loop, yet the ball comes out relatively dead, causing havoc for your opponent. It's usually done against backspin, where you are both close to the table (so the opponent has less time to recognize the lack of spin), and where the opponent has a reasonable expectation of extreme topspin (since you are continuing the spin when you loop against backspin, using the incoming spin to add to your own).
Some players dummy loop by contacting the ball closer to the handle, while contacting the ball closer to the tip for maximum spin. It's a little trickier this way, but can be even harder for an opponent to see the difference. How many opponents can tell whether your loop contact was near the tip or handle?
A key point of all dummy loops - do the shot with a full swing, with full enthusiasm, as if you were really going for your spinniest loop. If you hold back on spin by holding back on the stroke itself, the opponent will easily see that. It's also important to keep the ball deep. That way, if the opponent does reacts to the lack of spin, he probably won't be able to hammer a winner off it, which is much easier to do against a ball that lands short. Even a ball with light topspin can be effective if it goes deep.
Against a primarily defensive player, where there's little risk of them effectively attacking your dummy loop, you should constantly vary your spin from heavy topspin to dead dummy loops. The change of spin will mess up a chopper or blocker more than just extreme topspin.
It's fun watching an opponent block into the net, and stare at his paddle in disbelief!