One of the most under-utilized serves is the short serve to the forehand from the backhand side. Most players serve from the backhand side since this puts them in position to follow their serve with a forehand if there's a weak return. However, far too often players do this serve over and over crosscourt to the opponent's backhand. This makes it easier for the receiver to get into a rhythm and make effective returns. Instead, try serving short to the forehand. There are numerous advantages to this serve and only a few disadvantages.

The most common serves from the backhand side that go short to the forehand are the forehand pendulum and reverse pendulum serves, the backhand serve, and the forehand tomahawk serve. Pendulum serves are forehand serves with the racket tip down. Normally the racket goes right to left for a righty (with contact on the left side of the ball), but for a reverse pendulum serve it goes left to right (contact on the right side of the ball), which is awkward for many players starting out. Forehand tomahawk serves are done with the racket tip up, with racket going from left to right (contact on the right side of the ball). Some players do reverse tomahawk serves, with the racket moving right to left (and contact on the left side of the ball), and hitting the ball with the backhand side of the racket. Backhand serves are usually done with the racket moving left to right (with contact on the right side of the ball). Backhand serves are easier to keep low and short, but often have less variety than pendulum serves, where it's easier to go either direction at contact and to do subtle changes to vary the spin. Tomahawk serves are relatively easy to keep short, but are more difficult to serve with heavy backspin, and so are often predictably sidespin and topspin variations.

Left-to-right sidespins (i.e. backhand serves, tomahawk serves, and reverse pendulum serves) are often more effective since the sidespin requires the receiver to aim down the line, which is awkward to do when receiving a short ball with the forehand. When a receiver reaches in with the forehand it's easier to aim crosscourt, which is the direction you want to aim to compensate for a forehand pendulum serve.

Here are the advantages and disadvantages of serving short to the forehand. (We're assuming two righties for this, but most applies to lefties as well.)

Advantages

1. It's a variation that throws the receiver off from the more common serves into the backhand.
2. Most players find receiving short balls to the forehand somewhat awkward with their forehand. In fact, many will try to receive this with their backhand. If so, then angle it even more to the forehand side (if necessary, serve more from the middle of the table, or even from the forehand side), or throw in deep serves to the backhand to keep them in position.
3. Many receivers cannot forehand receive down the line against a ball short to their forehand, and you get a predictable return to your forehand.
4. It draws the receiver in over the table, giving the server the opportunity to jam him on the next shot, either to the wide angles or middle.
5. Against a player with a strong forehand but weaker backhand, a short serve to the forehand draws him in over the table, leaving him vulnerable on the backhand on the next shot.
6. It's a shorter distance to the opponent's side than going crosscourt, and so rushes the opponent.
7. You are closer to the net when serving down the line, and so it's easier to serve low, since your target is closer.
8. You can throw in short serves to the middle as a variation. If the receiver has been receiving short balls with his forehand, he may find this change awkward if he's already looking to receive with the forehand.

Disadvantages

1. It gives the receiver an angle into the server's wide forehand. This can leave the server vulnerable into two ways, to a wide-angled return to the forehand, or if the server moves over to cover the wide forehand, he may leave himself open on the backhand. (But see #3 above.)
2. It's tricky keeping this serve short since you have less table than if you go crosscourt, and if it goes long, it's often an easy ball for the receiver to forehand loop.
3. Since you usually don't want to serve long to the receiver's forehand (an easy ball to loop for most players), serves to the forehand tend to be short, while you can get away with long serves to the backhand more often (since most players don't backhand loop as well). This cuts down on the variety of serves you can do to the forehand.