Addition Cocktail Spice is just what the name implies: spice for cocktails. The company's products are similar to bitters in terms of aromatic potency, but has no bittering agents. While most are simply single-ingredient tinctures, try hunting down better ingredients and getting a better extraction than the spice geeks at Addition.
Some of these spices, such as the Pink Pepper and Turmeric, are useful primarily as aromatics, since they have big noses but subtle flavor. Others, such the Black Pepper and Piri Piri, offer a lot more heat and flavor than they do aromatics. Still more spices, like Cardamom, Garlic, Rosemary, and Thai Chili, have a big impact on both nose and mouth.