negotiator (n.)

• agent
• arbitrator
• bargainer
• broker
• cardholder
• connection
• contact
• deputy
• front
• go-between
• intercessor
• intermediary
• intermediate
• intermediator
• intermedium
• internuncio
• mediator
• medium
• middleman
• mouthpiece
• negotiant
• negotiatress
• negotiatrix
• ombudsman
• organizer
• spokesman
• spokeswoman
• unionist