What is the most difficult pest you deal with in your garden?

Leaf miners love my tomatoes and white fly gets the plumeria and areca palms. Rust gets the pikake and black spot gets the sunflowers. I haven't determined what is getting the gardenia or the lantana, I think there are at least two different things at work but I'm treating them with neem oil and the jury is still out. Slugs and snails aren't a problem only because I'm container gardening. Oh yeah, the birds get the papaya if some weird disease doesn't get them first. It's a jungle out there.