There are so many plants, edible and not, in my garden that I consider indispensable, but I do especially adore figs and I am a bit of a peony addict.
Regret is salad burnet, as it's not really that tasty to me and I've seen it establishing itself off of my property in wild areas near my home and I think it came from my garden, oops! Elecampane comes in second, with lemon balm holding a solid 3rd place, or maybe fennel...haha.
Blackberries, ivy, and vinca weren't my fault but goodness they are tough!
It would be neat to be able to grow pomegranate, avocado and coffee, as others have mentioned, but if it was warm enough for those, I wouldn't have so many of my other favorite things that need a cold winter, so I really don't mind buying those items at the store.