Thai Dry Chili Paste
Trader Joe's makes an easily accessible version, but you can also pick up a jar at your local Asian market. The flavor profile is much milder than a Sriracha or Gochujang paste and it brings a smokey, earthy note to your food. Try a tablespoon in your next stir fry or mix it into ground beef for burgers with a little kick.
Horseradish brings it's own, unique "bite" to food and I've learned that most people have a love/hate relationship with it... personally, I'm on the love side. While too much can ensue a nasal-clearing sensation, just a little bit tossed into a marinade for chicken will really take a basic grilled meat to the next level.
Porcini Mushroom Powder
I adore mushrooms, but once you get past the basic white variety, they can get pretty pricey. Next time you're walking through the produce section, look for the rack of dried mushrooms - they're a solid value and they don't spoil so you can store them in your pantry for whenever you need them. White button mushrooms can be a little blah, however if you dust them with a tablespoon of porcini powder, you can elevate them to a higher status. Try sautéing with some sliced onions and a bit of olive oil for a delicious topping on your next steak.
Anytime I'm looking to add a touch of acid to a dish to balance it out, I nearly always start with sherry vinegar. It's a great balance of tart with a touch of sweet and the subtle wine notes compliment most dishes quite well. It's versatile enough to work in everything from salad dressing to marinades. After cooking over easy eggs, try add a tablespoon to the skillet to deglaze the pan and pour it over your eggs for a lightly tangy kick.