Let’s see… in chronological order:
1987: Williams FW11B. 1-2 in the drivers championship, almost double the points of McLaren in the constructors standings.
1988: McLaren MP4/4. Won every race except Monza, and that was due to a stupid and unfortunate accident.
1991/1992/1993: Williams FW14, FW14B, FW15C. Okay, this is three different cars, but it’s basically the same model. If I have to choose one, it’s the ’92 FW14B: the fastest and most dominant car in the early 90s. Senna won the championship in ’91 due to numerous retirements by Mansell, but in ’92 Williams was unbeatable. in ’93 not so much, as other teams finally caught up with the technical expertise of Williams.
1995: Benetton B195. After San Marino, it looked like Hill would take the title. But Schumacher and Benetton turned it around, and duly took both the titles.
1999: McLaren MP4/14. I always considered this to be the fastest of the late 90′s McLarens. Sure, in 1998 The MP4/13 won the opening race in Melbourne by a lap, but in 1999, it was only by Häkkinen’s misfortunes that others could challenge him.
2002: Ferrari F2002. The car that caused some massive rule changes to be made. That’s what I call dominance.
2004: Ferrari F2004. Best car for most of the season, but slipped away in the end once the titles were wrapped up.
2005: McLaren MP4-20. Based purely on speed, this car usually destroyed the Renaults – before developing some mechanical gremlin (Kimi) or crashing out (JPM).
2009: Brawn BGP 001. The ultimate double diffuser car.
2011: Red Bull RB7. The quickest car for almost the entire season. Not by much, but a small margin is enough.
And a honourable mention goes to the 2007 McFerrari spygate car :P