Marigolds - The marigold is probably the most well known plant for repelling insects. French marigolds repel whiteflies and kill bad nematodes. Mexican marigolds are said to offend a host of destructive insects and wild rabbits as well. If you choose marigolds for your garden they must be scented to work as a repellant. And while this plant drives away many bad bugs, it also attracts spider mites and snails.
A side note:
This is the first year I've had serious neighbor cat(s) problems in my back yard. It is also the first year I haven't planted marigolds in the garden.
No, they don't smell pleasant. But, it is better than cat feces. And they look a LOT better.
Cheers,
PS:There are a lot of companion plants out there.
You can intersperse them with other desirable plants for symbiotic relationships.
Example: First year of tomato growing had the crop devasted by Hornworm.
Since companion planting basil next to them, I haven't seen a tomato Hornworm in 15 years.