A long-standing favorite dating back to the late 1890s, Kitchen Boquet became very popular in the 1940s and 1950s. Less of a seasoning than a browning additive, it is great for roasts and to make gravy from pan drippings. Not much else, though.
Its primary ingredient is caramel, which is the browning agent. This makes meats and other foods look browned, when they really aren't. Some people baste it onto microwaved food to allow the food to look more traditionally-browned and not so "blah" and anemic. Kitchen Bouquet also contains onions, parsnips, carrots, celery, parsley, and turnips, in addition to some spices. But its real beauty is in making foods just look better. The liquid isn't particularly flavorful unto itself. Smelling Kitchen Bouquet doesn't give any real sense of ingredients, either. This is why I say it's mostly for appearance's sake, and not some fabulous flavoring additive.
Admittedly, I will use a bit of Kitchen Bouquet in gravies and on the occasional roast, but not much else. A single 4-ounce bottle has lasted well over 10 years in my home. So, another plus is its shelf-life! If I use it, I pre-season the meat before applying the liquid to the roast.