I always ask the photographer if they have the ability to do a magic shot. They may also know which photographers around the park can do magic shots.
I know the Tinkerbell in the hand is the most common in many different places. I have also gotten Stitch coming out of the ground at the floral Mickey, I got Mickey balloons at the stationary tea cup in Fantasyland, I got Captain Hook in front of Rivers of America (this was the only time I have seen it), and I can't recall any others at this moment. I'm sure I have gotten more though.