cross-examiner, cross-questioner - someone who questions a witness carefully (especially about testimony given earlier)

examiner, quizzer, tester - someone who administers a test to determine your qualifications

inquisitor, interrogator - a questioner who is excessively harsh

interviewer - a person who conducts an interview

headcounter, poll taker, pollster, canvasser - someone who conducts surveys of public opinion; "a pollster conducts public opinion polls"; "a headcounter counts heads"

speaker, talker, verbaliser, verbalizer, utterer - someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous); "the speaker at commencement"; "an utterer of useful maxims"