I couldn't choose favorites, though of my herbs, basil and Thai basil would be my favorites, and these are what made me set up my hydroponics, so that I could always have them. Then there are the ones that I had to grow, because I couldn't find them anywhere back then - kaffir lime leaves and curry leaves. Sage, bay, rosemary, thyme, dill, parsley, chives, and garlic chives I also have out there, and probably something I have forgotten! lol
Chili peppers are my most used spice, with probably Thai peppers my most used, since I use them in Thai, Chinese, Indian, and Mexican, in place of similar small, hot varieties, and I grind them up, to use as cayenne, with more flavor. I have over 30 types of dried chiles in my pantry.
Cumin and coriander would probably be tied for second, and I buy those by the pound, keeping the extra in foodsaver bags, refilling the jars as necessary, and re-sealing the bags.
In my Indian cooking I've found some unusual spices, which I use frequently in other cuisines. One is Black Cardamom, which has an unusual, smoky flavor, and I often crack those, and put them in a small tea ball, and boil them with beans or grains, to get that aroma. And another, which sounds crazy, is Asafoetida, a.k.a. Hing, which I often use when simmering some beans or lentils, in place of putting a whole onion in the pot. It doesn't smell like it, at first (it's actually disgusting, thus the name), but when finished, it smells, and tastes, like an onion was simmered with it! Easier, and cheaper, as well.
Sambar masala is my favorite spice mix. Garam masala is called for a lot, but in smaller amounts, so I make less of it. There are several more that I make, come fall (mostly used in cold weather foods), but these are the two, besides a basic curry powder, that I always have, even in the summer.