Just Deserts

Here's one I would have gotten wrong, I would have bet everything I had that it was "just desserts" and not "just deserts". "Just desserts" makes a kind of sense, the nefarious evil-doers got their comeuppance using a "have their cake and eat it too" metaphor. What's even more confusing is that it is not pronounced like the noun form of desert (a barren or desolate area), but rather like dessert (a usually sweet dish served at the end of a meal) with the emphasis on the second syllable, or the verb form of desert (to leave empty or alone; abandon).

There's a discussion of it here.