Farhan Zaidi is just the latest MLB figure to swap sides of a bitter rivalry

On Tuesday, the Giants announced that they'd found their new president of baseball operations: former Dodgers GM Farhan Zaidi. While the move is guaranteed to make Hot Stove season at least 300 percent more intriguing, it's also hardly the first time that a prominent MLB figure -- players, managers or executives -- have made the leap from one team to its most bitter rival. 
Let's look at a few others:
Cubs-Cardinals
Lou Brock
"Thank you, thank you, oh, you lovely St. Louis Cardinals. Nice doing business with you. Please call again any time." That was how Chicago Daily News scribe Bob Smith led off his column on June 16, 1964. The Cubs had just acquired Cardinals starter Ernie Broglio, whose 2.99 ERA was just the sort of pitching depth Chicago needed to finally get over the hump in the National League. The best part? They didn't even have to give up much, only a 24-year-old outfielder who'd hit .251 the year prior ... by the name of Lou Brock.

The rest, of course, is history: Brock took off when he got to St. Louis, .348 with 33 steals down the stretch to help the Cards win the World Series (and kick-start what would become a Hall of Fame career). The Cubs, meanwhile, spent the rest of the decade a piece away from reaching the Fall Classic.
Bruce Sutter/Lee Smith
Sutter spent the first five years of his career with the Cubs, who traded him to their archrivals prior to the 1981 season ... which opened the door for another legendary closer, Smith, who anchored Chicago's bullpen until 1987 (and remains the team's all-time saves leader). 
Harry Caray
You didn't think that arguably the fiercest rivalry in baseball would be limited only to the diamond, did you? Caray's become synonymous with the Cubs, but he spent the first 25 years of his broadcasting career as the voice of the Cardinals -- until the team let him go following the 1969 season. After stints with the A's and White Sox, he eventually found his way to the North Side, just in time to call the team's first trip to the postseason in 40 years:

Yankees-Red Sox
Babe Ruth
Perhaps you've heard about the time the best baseball player of all-time -- coming off a year in which he hit 322/.456/.657 while throwing 12 complete games! -- was traded from one rival to the other, touching off an 86-year title drought. If not, well, here you go.
Roger Clemens
Unlike the previous entries on this list, Clemens didn't go directly from Boston to New York. After spending the first 13 years of his career with the Red Sox, he signed with the Blue Jays in the winter of 1996, and proceeded to put up two Cy Young seasons in Toronto -- along with one all-time revenge game:

But the Jays still struggled to compete, and so the Rocket turned his eyes south -- to the Yankees, who he helped to World Series titles in 1999 and 2000.
Johnny Damon
Damon crushed the Yankees' dreams in the fall of 2004. But free agency is forever undefeated, and one year and a Steinbrenner bidding war later, he found himself in pinstripes -- leading to quite possibly the most jarring aesthetic transition in baseball history:

Damon was a solid contributor in New York for four years, helping the team capture the 2009 World Series.
Wade Boggs
Speaking of Red Sox icons who then came to the Bronx and won it all: Boggs was arguably the best player of the 1980s, an excellent defensive third baseman who just so happened to be a perennial batting champion to boot. Despite all that talent, though, he couldn't get Boston over the hump -- so, with his career winding down at age 35, he signed with the up-and-coming Yankees.
He never recaptured his prime, but he did get that ring -- along with a celebratory lap atop a horse:

Dodgers-Giants
Then, finally, there's Dodgers-Giants, a rivalry that just had a whole fuel canister dumped on top of it -- not that it needed the help.

But Zaidi is hardly the first person to switch sides, as the examples below show. (And that's not even counting all the players -- from Orel Hershiser to Duke Snider to Juan Marichal -- who became legends with one team before briefly appearing with the other toward the end of their careers.)
Jeff Kent
After breaking in with the Mets, Kent blossomed into a star in San Francisco, the Robin to Barry Bonds' Batman, and won an NL MVP Award in 2000. Even more importantly, he also helped bury the Dodgers down the stretch of the 1998 season:

A few years later, he'd find himself on the other side of the rivalry, spending the final four seasons of his career in L.A.
Dusty Baker
As a player, Baker was a Dodger through and through: He spent eight years in L.A. -- compared to just one in San Francisco, the penultimate season of his career -- and earned two All-Star nods while helping to capture the 1981 World Series (and probably inventing the high-five). Of course, after he retired, things got a bit more complicated.
Baker began as a first-base coach in San Francisco, then worked his way up to hitting coach, and then, in 1993, the Giants named him manager. He won pennants in 1997 and 2000, taking home NL Manager of the Year honors, before guiding the team all the way to Game 7 of the World Series in 2002. As for whether that resume makes him more of a Giant than a Dodger, well, we'll let each side debate that one.