debater (n.)

• apologist
• arguer
• casuist
• controversialist
• demagogue
• disputant
• haranguer
• logomachist
• panelist
• polemic
• polemicist
• polemist
• rabble-rouser
• ranter
• speaker
• speechifier
• speechmaker
• spokesman
• spokeswoman
• spouter
• talker
• tub-thumper
• wrangler