petitioner, suppliant, supplicant

one praying humbly for something; "a suppliant for her favors"

• besieger — an energetic petitioner
• postulant — one submitting a request or application especially one seeking admission into a religious order
• solicitor, canvasser — a petitioner who solicits contributions or trade or votes

• applicant, applier — a person who requests or seeks something such as assistance or employment or admission