As this year's Stanley Cup finals is coming to a close, It was posted that on June 22nd 2010 the Bruins completed a trade that brought Nathan Horton and Gregory Campbell to Bruins that changed the team completely.
This trade gave the foundation for the future Stanley Cup winning Bruins in 2011 as Nathan Horton was a key factor in bringing the cup back to Boston. During the series against the Vancouver Canucks, the Bruins won the series in seven games.
The power of trades can certainly be seen throughout the league and the Panthers who are currently in the finals saw that when they made their deal with the Calgary Flames bringing Matthew Tkachuk to the team which changed the dynamic and brought a physicality to their game which has propelled then to the finals two years in a row.