A good quality set of knives is what many professional chefs say is the most important equipment to have in your kitchen.
But if you've been using some of your knives interchangeably, then stop at once as each blade is designed for different and very specific tasks.
Chef's Knife: Multi-purpose, but mainly used for cutting meat, dicing vegetables and disjointing large cuts.
Utility Knife: Slicing herbs, chopping vegetables, and slicing bagels and buns.
Bread Knife: Slicing bread, cake and thick-skinned fruits such as tomatoes and peaches.
Carving Knife: Carving large and dense pieces of meat, including roast chicken breast and beef
Cleaver: Splitting meat and bone, preparing shellfish such as lobster, and crushing garlic using broad side
Mezzaluna: Mincing herbs and vegetables
Fillet Knife: Removing bones from fish, and de-boning other cuts of meat
Santoku: Slicing cheese and meat, chopping vegetables, dicing onions
Cheese Knife: Slicing cheese
Sashimi: Cutting fish for use in sushi