No. 1: Brad Marchand
I'm not sure if there is a player who is more disliked than Brad Marchand, however, if he joined the Leafs, I can't think of a player who fans would turn their opinion on quicker. Marchand is the definition of the player who you hate to play against, but would love on your team, so him joining the "darkside" would be incredible for Leafs fans.
Marchand is currently in the last year of his $6.125M contract, and although it feels like he'll retire as a member of the Boston Bruins, there have been plenty of rumors of the team making a move. The Bruins have been one of the most consistent NHL franchises over the past 20 years, having only missed the playoffs four times since 2001, but that may be changing.
Patrice Bergeron and Zdeno Chara led the team for years, but with those two retiring, the new core of David Pastrnak, Charlie McAvoy and Marchand haven't quite lived up to expectations. With the team potentially headed towards missing the playoffs for the first time since 2014, they may look to unload their aging star for young assets.
Marchand may be 37 years old, but he's still delivering at the highest stage, as shown by his recent performance at the Four Nations Face-Off and regular season play. Toronto's left-side has been pretty good as of late, led by Matthew Knies and Bobby McMann, but we all know the team can't rely on that in the playoffs and could use a true playoff performer like Marchand to get them over the hump.
Marchand is not only a fierce competitor in the playoffs, but has 56 goals and 138 points in 157 career playoff games (via: hockeydb.com), which means he always comes up clutch in the biggest moments. The Leafs have gifted the Bruins way too many things (Tuuka Rask trade, multiple Game 7 losses) that it's time for Boston to finally repay Toronto, so if the team acquired Marchand and it guided them to a Stanley Cup, I'd call it even.