Amid speculations about the futures of Hamilton, Räikkönen and Vettel I made a decision to compile the drivers who have won on their debuts for their new teams:
Giuseppe Farina, Great Britain 1950, Alfa Romeo
Fairly natural that the first ever WDC Grand Prix was won by a driver. Had been an Alfetta driver before so not really his first Grand Prix for them as far as I'm aware.
Juan Manuel Fangio, France 1954, Mercedes
Merc made their return to Grand Prix racing in style, with Fangio leading home team mate Karl Kling in a formation finish.
Fangio/Musso, Argentina 1956, Ferrari
This is one of the strangest anomalies ever. Two new drivers to Ferrari in a car designed by Lancia sharing the same car to win Fangio's home race. Incredible!
(Juan Manuel Fangio, Argentina 1957, Maserati)
Not really the first race for him with Maserati, since he raced there in 1953, but still a win immediately after a switch of teams. Depends on what the criteria is.
Stirling Moss, Argentina 1958, Cooper
Moss won in a 10-car field for Cooper. Vanwall didn't bother enter the South American race to Moss went there with a Cooper instead and won the least contested World Championship Grand Prix ever. A poor start to the newly-invented Constructors Championship with a mere three makes taking part.
Maurice Trintignant, Monaco 1958, Cooper
Trintignant took one of the most fortunate ever victories, with Jean Behra, Stirling Moss and Mike Hawthorn all breaking down in front of him. This added Trintignant to the exclusive club of multiple winners of Monaco. Astonishingly, that's two more than what Jim Clark ever won!
Giancarlo Baghetti, France 1961, Ferrari
To this day the only driver to win on his World Championship debut if first-ever-race-contenders are disqualified. Won a drag race by a mere tenth down the start and finish-straight against Dan Gurney's Porsche.
Pedro Rodríguez, South Africa 1967, Cooper
Rodríguez beat fellow Cooper driver, local star John Love, to win the 1967 season opener, marking his switch to Cooper. However, he couldn't follow this up by a championship run.
Mario Andretti, South Africa 1971, Ferrari
Andretti guested for Ferrari and starred to take the Kyalami victory, his first of many, but ultimately the only win he ever took as a Ferrari driver.
Jody Scheckter, Argentina 1977, Wolf
Coming off the back of a season dominated by Lauda and Hunt, Scheckter took a surprise opening salvo on his run to 2nd in the WDC with the new constructor Wolf. Being beaten by Lauda and Ferrari over the season, the new team still took a staggering 5 podium in the first six races with the one-car operation.
(Alain Prost, Brazil 1984, McLaren)
Prost was not a real first-time winner, since he drove for McLaren in 1980, but his 1984 win in Brazil marked a debut win for the second partnership that was to last six years and yield three titles, before the Senna feud prompted him to sign with Ferrari. Prost was the benchmark driver in the mid 80-s and this was the ideal start for him at McLaren - but ultimately Lauda made him wait to 1985 for his first world title.
Nelson Piquet, Brazil 1986, Williams
The stuff dreams are made of for Nelson, who marked his Williams switch by defeating São Paulo-born nemesis Ayrton Senna in his beloved Rio de Janeiro.
Nigel Mansell, Brazil 1989, Ferrari
The one race where his paddleshift gearbox didn't break down in the first half of 1989 was in Rio de Janeiro, where Mansell won his first Ferrari race, passning the 'invincible' McLaren of Alain Prost on the way.
Alain Prost, South Africa 1993, Williams
Prost inherited the active-suspension Newey-designed Williams concept that had completely obliterated the field in the 1992 season with Mansell at the wheel. Therefore it was no real surprise that the Professor could guide the blue and yellow car to P1 in South Africa, with Ayrton Senna almost a lap down. In spite of a gritty season from Senna which saw him lead after Monaco, Prost's championship was rarely in doubt.
Giancarlo Fisichella, Australia 2005, Renault
Villeneuve went close in 1996 for Williams, but it took until 2005 until the achievement was done again, this time by Giancarlo Fisichella, who was the only driver with a competitive car lucking in to decent rainfall in the first of the twin sessions of qualifying. Ferrari driver Barrichello and team mate Alonso looked quick in race conditions but ultimately Fisichella could've been pacing himself.
Kimi Räikkönen, Australia 2007, Ferrari
One of the most dominant performances seen in a post Schumacher-era dry race by any driver. Kimi set a fastest lap a full second faster than the rest of the field to win on his Ferrari debut, marking a perfect start to the up and down-season that ended on a high with his sole championship to date. Since the floor of the Ferrari was banned post-race, the dominance evaporated and a season-long battle with team mate Massa and McLaren duo Hamilton and Alonso ensued.
(Jenson Button, Australia 2009, Brawn)
He didn't change workplace, they just switched livery and engine from Honda. So it's fine to count it if you want to, but I don't see that as a new driver at a team-victory. It was a new team, but not a new driver. Nevertheless, a safe pair of hands throughout that day from Button who went on to become champion that year.
Fernando Alonso, Bahrain 2010, Ferrari
Alonso was outqualified by Massa and made a brave move into Turn 2 to take second, but seemed unable to do anything about leader Sebastian Vettel. Then the German suffered from car issues and fell back to 4th, ensuring Alonso won on his Ferrari debut. The victory was particularly sweet for Alonso following the Crashgate controversy and the ousting of Räikkönen in favour of himself. Ultimately it was not enough to claim the 2010 crown, but Alonso still had a season with some real highs, including a Monza win and a fair and square beating of Vettel at Singapore.
Hope you've enjoyed it and feel free to add if I've missed someone