Basil is an amazing companion herb. It has a lot going for it such as repelling aphids, thrips, and spider mites PLUS it can improve the flavor of some of your crops!
Chives is part of the allium family and can deter pests such as aphids, flies, and beetles. It can also improve the flavor of crops like tomatoes.
When you think of dill, you might think of pickles. But dill is a great companion for cucumbers even before they come together in pickles.
Like many herbs, sage is great for both repelling pest insects such as flea beetles and cabbage butterflies, and attracting the beneficial ones.