Synergy is pushing the debate on its website. Dominic Curran, the agency's deputy MD, said: "This is not about the biggest financial deals but decisions made off the field that were genuine game changers in the wider sports marketplace. The debate began on a long car journey and then continued at the agency."
Curran said: "We brought the debate back to Synergy and found the more we’ve all discussed it, the more we’ve argued and the more we’ve argued, the more we’ve enjoyed it. So we thought it was only fair to open the debate up."
Synergy will publish all contributors' lists, from which a top 10 will be selected.
Whoever correctly predicts the top position will be put into a draw for a Fortnum & Mason Christmas hamper.
Potential candidates include Jack Nicklaus successfully arguing for the inclusion of Europe in the Ryder Cup, and the (then struggling) sports shoe company, Nike, signing rookie Michael Jordan and creating The Air Jordan, the first shoe to be named after a player.
Other iconic events in sports marketing include the English First Division football clubs resigning en-masse from the Football League and forming the Premier League, the first Extreme Games event, and the phenomenon that is the Red Bull brand.
If you would like to know what the experts think, for some ideas.
The blog includes comments from: Ralf Hussmann, Global Sports Marketing Director BMW; Lee Bailey, Guinness GB Sponsorship Manager; Ashling O'Connor, The Times; Roger Blitz, FT; Paul Vaughan, RFU Commercial Director; John Feehan, CEO Six Nations/British Lions; and the man most agree created modern sponsorship, Patrick Nally.
You can post your thoughts through Brand Republic below this story.