straight man (n.)

• actor
• actress
• antagonist
• barnstormer
• character
• feeder
• foil
• heavy
• histrion
• ingenue
• juvenile
• mime
• mimer
• mimic
• monologist
• mummer
• pantomime
• pantomimist
• playactor
• player
• reciter
• soubrette
• stooge
• stroller
• theatrical
• thespian
• trouper
• villain