What is the best exercise to target abdominal fat?

See, there is not any workout that is going to target extra flab in the stomach area. While it hasn't been proven beyond the remotest shadow of a doubt, I believe you cannot focus on burning fat in a specific area.

If there is fat remaining, the only way to get rid of it is to lose more fat. And you can't target that - the body burns fat in its own order. So you can do all the crunches, Swiss ball workouts, weighted ab machines in the world, and it won't reveal your abs - the place to look is your nutrition. Clean it up, tighten it up, ramp it down, and lose the fat, and eventually you will reveal those abs.