Question: has vegeta ever said goku?
Answer: He is more widely known as Goku, as that is the name he was raised with. ... So when Vegeta says Kakarot, he is calling Goku by his name. Now, to answer your question: The only instance I could recall in which Vegeta says the name “Goku” is in Episode 110 of Dragon Ball Z - Battle in Kami's Lookout, during the Garlic Jr.