For filleting fish, slicing vegetables and ginger as thin as possible, and general all-purpose Japanese cutting tasks, the best tools to use are sushi knives. A variety of Japanese knives are available for sushi related tasks, such as thin slicing of fish for sashimi, beheading of fish, preparation of thinly-sliced vegetables and fruits and cutting of a sushi roll.
For the thinnest of produce slicing tasks, look for an usuba or nikiri style sushi knife. These are designed to produce very thin cuts, so that vegetables and fruits can be cut as thin as a piece of sashimi. Many of these knives are ground on only one side of the blade to aid in thin slicing. Keep in mind that these knives are generally only suitable for right-handed or left-handed chefs, depending on which side of the blade is ground.
If you are looking for sushi knives that can cut fish very thin, go with a sashimi knife. They are designed to cut the fish while it is being pulled toward the chef. They have ultra-thin blade edges to accomplish this task. For beheading the fish before it is filleted, look for a specialty sushi tool known as a deba knife.