Such tactics fail the ethics test. As far as I'm concerned, there's only one honorable way to unhinge your opponent: with your shots.
Your opponent might get upset if you hit clean winners, but he'll get more frustrated if you make him miss what seems to him to be a perfectly hittable ball. When you win a point this way, you often win a few more as a bonus, because your opponent keeps thinking about the one he "should have had."
Here are my five favorite shots that tend to make opponents miss what seem to them to be easy balls:
1. Sidespin backhand:
If you already know how to hit a backspin backhand, which is what most people mean when they talk about a "slice backhand," you should be able quickly to learn a backhand that has a mixture of backspin and sidespin. The advantage of sidespin is that it makes the ball skid left or right on the bounce. If your opponent isn't used to this, she'll find herself suddenly too far, or, better for you, too close to the ball just as she's about to swing. Either way, she'll often hit a weak floater or dump the ball into the net. Learn the slice backhand here.
2. High, deep topspin:
During the 1970s, a new type of player emerged who drove everyone nuts.
The "moonballers" hit virtually nothing but this high, deep topspin that few players could find a way to attack. When two pro moonballers got matched up for singles, individual points would sometimes go on for several minutes, eventually drawing boos from the impatient crowd. In the pro ranks today, most players have developed effective countermeasures, so the moonball is less often used, but if you're playing below the pro ranks, your opponents might not have an answer. The moonball is a difficult shot to attack because it's deep and it kicks above the height at which most players can hit hard. It's also highly reliable, so you can keep hitting it until your opponent loses patience and risks a low-percentage shot. If you learn a topspin lob, you'll have your opponents ready to howl at the moon in no time.