I'm a big fan of using as much as possible from food.
I eat potato skins, bacon fat and pizza crusts, the latter ideally dipped in something (hot sauce or caesar salad dressing are good).
I also eat the garnishes in restaurants - the bits of raw kale or lemon slice, or shiso leaves they decorate dishes with.
I adore sunflower seeds, and really miss them were I live. Part of the appeal is the slow process of eating them, as it makes the snacking experience last a long time for the amount of calories. I spit the seeds out. My favourite are Spitz (a Canadian brand) is seasoned or chili-lime flavour. However, I am always really, really careful to seal the bag when not using, as cockroaches taste nothing like sunflower seeds.
Cooking wise, I save the seeds when cooking pumpkin or winter squash and roast them for snacks. I will happily eat the tops of beets, steamed, with vinegar. When I peel and seed tomatoes I toss the seeds and peel in a bag for use when making soup stocks (along with the tough stems of dried mushrooms, random meat bits like chicken backs, feet and heads). I save the liquid from cooking dried beans, as it's great in soups, and adds rich flavour to vegetarian soups and stews. The whey left over from making paneer or yoghurt cheese gets used in soups or instead of water when making bread. I also save and strain bacon fat, the fat from roasting pork belly, goose fat and the better chicken fat for culinary use. The rind from parmesan goes into tomato soups. And stale bread goes into breadcrumbs, croutons, bread soup, bread pudding or bruschetta, depending on the type of bread.
And my own personal quirk is to eat the skin of lemons and limes. I just like the taste.