There aren't many, if any, genuine Greek words beginning with the letter "f". Ancient Greek did not have the phoneme /f/. Words that appear to start with "f" in English transliterations are usually borrowed from other languages (like Latin or through Latin from other languages) or are a result of spelling conventions.
So, the answer is essentially none. Any word seeming to begin with "f" in a Greek context likely has a different original sound and spelling.