Marian Hossa, Zdeno Chara

NHL general managers are poised to go shopping when free agency opens July 1.
Signing free agents allows GMs to bring in talent without having to compensate another club, as they would in a trade. The best signings are the ones that take a negative and turn it into a positive; however, these also tend to be the rarest.
Among the hundreds of players who have changed teams via free agency, here are 10 of the best signings during the past 10 years:

Zdeno Chara, Boston Bruins (2006) - The Ottawa Senators decided after the 2005-06 season that they could keep either Wade Redden or Zdeno Chara, but not both. They opted for Redden, and the Boston Bruins were more than happy to sign Chara to a five-year contract. By the end of that deal, Chara, as Boston's captain, was accepting the Stanley Cup from NHL Commissioner Gary Bettman after the Bruins ended a 39-year championship drought in 2011.
Chara then signed a seven-year contract with the Bruins that will keep him in Boston through the 2017-18 season. He won the Norris Trophy in 2009, the Hardest Shot contest during the All-Star Skills competition five times in a row (2007-2012) and has been one of the NHL's best defenseman for most of the past decade.

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Brian Rafalski, Detroit Red Wings (2007) - Rafalski had won the Stanley Cup twice during seven seasons with the New Jersey Devils. But the native of Dearborn, Mich., came home after the 2006-07 season, signing a five-year contract with the Detroit Red Wings. Rafalski turned out to be an excellent partner for Nicklas Lidstrom. He helped the Red Wings win the Stanley Cup in 2008 and get to Game 7 of the Cup Final in 2009.
He played four seasons with Detroit before deciding to retire at age 37, partly due to knee and back injuries. Rafalski had 35 goals, 169 assists and a plus-78 rating in 292 regular-season games with Detroit, and was a top-10 finisher in the balloting for the Norris Trophy twice during his time with the Red Wings. The three-time Stanley Cup winner was elected to the U.S. Hockey Hall of Fame in 2014.
Anton Stralman, Tampa Bay Lightning (2014) - Stralman never put up big offensive numbers during the first seven seasons of his NHL career, but he quietly became one of the League's most effective defenseman after joining the New York Rangers in the fall of 2011. He became a free agent after his third season in New York, and the Lightning wasted little time signing him to a five-year contract. If anything, Stralman has been even better since joining the Lightning; he's had his two best offensive seasons and has teamed with regular partner Victor Hedman to form one of the NHL's best defensive pairings.

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Brian Elliott, St. Louis Blues (2011) - Elliott was coming off arguably the worst season of his NHL career when he reached free agency in the summer of 2011, and the Blues were able to sign him to a one-year, two-way contract. Elliott repaid St. Louis by going 23-10-4 with a 1.56 goals-against average and a save percentage of .940 in 38 games. He ended up spending five seasons with the Blues, going 104-46-16 - his worst goals-against average during that span was 2.28. Elliott formed a solid combination in goal with Jaroslav Halak, Ryan Miller and Jake Allen before being traded to the Calgary Flames on June 24.
Marian Hossa, Chicago Blackhawks (2009) - It took a second bite of the free agency apple for Hossa to win the Stanley Cup. He had signed a one-year contract with Detroit in the summer of 2008 after the Red Wings defeated Hossa and the Pittsburgh Penguins in the Stanley Cup Final. However, the Penguins got even in 2009, with Hossa on the losing side again.
He went back on the free agent market and joined the Blackhawks in 2009, signing a 12-year contract. Since then, he's been a key contributor to a team that has won the Cup three times in six seasons, helping Chicago end a 49-year Cup drought in 2010. Hossa has 160 goals and 370 points in 461 games in seven seasons with Chicago, and the first goal he scores next season will be the 500th of his career.

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Petr Sykora, Pittsburgh Penguins (2007) - Pittsburgh signed Sykora, an 11-time 20-goal scorer, to a two-year contract in the summer of 2007 to provide secondary scoring behind Sidney Crosby. He did just that. Playing on a line with Evgeni Malkin, he scored 28 goals and finished with 63 points in 2007-08, then scored a goal in triple overtime in Game 5 of the Stanley Cup Final against the Detroit Red Wings. Sykora scored 25 goals in 2008-09 and was a member of the Penguins team that avenged their Cup Final loss to the Red Wings the previous year. Sykora moved on in the summer of 2009, but not before he got to drink from the Cup.
Marian Gaborik, New York Rangers (2009) - The Rangers were looking for offense when they signed Gaborik, then 27, to a five-year contract. Gaborik matched his career-high with 42 goals in his first season in New York, dropped to 22 in 2010-11, when he missed 20 games with injuries, and rebounded with 41 goals in 2011-12, helping the Rangers win the Presidents' Trophy as the NHL's top regular-season team and advance to the Eastern Conference Final.
The Rangers traded Gaborik to the Columbus Blue Jackets prior to the 2013 NHL Trade Deadline, and he joined the Los Angeles Kings for their run to the 2014 Stanley Cup, but he hasn't produced the kind of numbers he did with the Rangers.

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Dominik Hasek, Detroit Red Wings (2006) - The Red Wings brought back Hasek, a six-time Vezina Trophy winner, at age 41 after he battled injuries while playing for the Ottawa Senators in 2005-06. He looked as good as ever in the next two seasons with the Red Wings, going 65-21-9 with goals-against averages of 2.05 in 2006-07 and 2.14 in 2007-08.
Hasek helped get Detroit to the Western Conference Final in 2007 and entered the 2008 Stanley Cup Playoffs as the starter but struggled and was supplanted by Chris Osgood, who earned the final 14 victories that brought the Cup back to Detroit.
Matt Moulson, New York Islanders (2009) - John Tavares came to the Islanders as the No. 1 pick in the 2009 NHL Draft, and that turned out to be good news for Moulson, who had known Tavares for much of his life. Tavares had played hockey and lacrosse with Moulson's younger brother in Mississauga, Ontario, and Moulson, a minor-league free agent, signed with the Islanders during the summer and developed instant chemistry with Tavares. He scored 30, 31 and 36 goals in his first three seasons with the Islanders, usually as Tavares' left wing.
Moulson had 44 points in 47 games in 2012-13, helping the Islanders reach the Stanley Cup Playoffs for the first time since 2007, but he was traded to the Buffalo Sabres for forward Thomas Vanek early in the following season.
Joel Ward, San Jose Sharks (2015) - Ward offered the combination of grit and scoring ability that the Sharks felt they needed after failing to make the Stanley Cup Playoffs in 2014-15, so they signed him to a three-year contract. He provided the kind of secondary scoring the Sharks had been missing, finishing with 21 goals and 43 points in 79 games this season while spending much of his time on the third line. Ward contributed seven goals and 13 points in 24 playoff games to help San Jose advance to the Stanley Cup Final for the first time in the franchise's 25-year history.