Doubanjiang (豆瓣酱) is my favorite. It's fermented black bean/soybean sauce that you can stirfry things with or just mix into already-cooked food. It doesn't have the same kind of funk that most fermented food has. I think it's fermented in the same way that soy sauce is fermented, so it's mostly just intensely salty.

My go-to brand is the Laoganma black bean sauce in chili oil. As you might expect, the chili oil gives it an extra kick. When I'm too lazy to make anything, I just mix a teaspoon or so into a bowl of rice and eat that.

You've probably heard of Marmite, but I'm also gonna recommend giving it a try if you never have. Usually I just put it on toast, but I've also mixed it into soup to add some umami. The best way I can describe the flavor of Marmite is also just really, really salty. In fact, when I spread it on toast, I try to spread it as thin as physically possible because it's easy to use too much. ^{Also, Marmite is superior to Vegemite. Sorry, Aussies.}