This is fairly random, but a few days ago a word thing occurred to me that Jed had brought up twenty years ago. That conversation was about the word cook, and how unusual it was. That is, for most activities (let’s call them verbs), the word for the person who does the activity has a suffix (such as -er) or other indication that it is a noun form. A person who bakes is a baker; a person who swims is a swimmer; a person who mocks is a mocker. But a person who cooks is a cook. Jed was asking for other examples, and I said that a fuck was someone who fucked, although generally, as it were, not to put too fine a point on it, up. This was not, alas, accepted.
At any rate, a few days ago I came up with one that it turns out is not on the Mark-Jason Dominus list of A(n) X Does X: monitor. So I thought I would open the whole question up to readers to see if there are still more.