Who do you want to visit? Note that this is an ambiguous sentence; it could mean who do you want to go see or who do you want to come see us. But if you make the normal contraction of “want to” to “wanna”, the ambiguity disappears. Mavens would solve the problem by insisting on “whom” in the first case and denying contractions like “wanna” as slovenly.
My restatement of a paragraph in Thinking Linguistically by Maya Honda and Wayne O’Neil.