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

Grasshoppers by the hundreds. Itty, bitty brown ones. The cat can't eat them fast enough. No bug sprays for me; I'm working on enriching the soil of my raised planter beds. So far I'm staying on top of the tomato worm problem. I'm getting better at finding them while they are still little. I prefer to drown them in a container of water rather than stomp them.