Companion plants

Hey everybody I've been reading about possible benefits from having small companion plants in with your grow. Does anybody do this and if so what's it doing for you? Basil in particular from what I've read is mostly good for pest control (specifically gnats) and just general health of the plant.

If you got run its always a cool thing but make sure you start the plants from seed or you may end up bringing in a pest or disease with a store bought plant.

Small herbs or succulents would be an easy go to plant. Cheers