Are there partnerships that win major events by using unpopular systems?
Barry Crane (originally Barry Cohen, the Detroit Demon) dominated many aspects of North American bridge for decades playing a system of weak openings and early exits from the auction. This was the antithesis of the systems being expounded by teachers such as Culbertson and Goren, which revolved around sound openings to assist average players in making their contracts, even if they often underbid.

Wealthy enough to be a client and strong enough to compete against the best, Crane inspired strong feelings, pro and con, amongst the North American bridge elite; but few dared cross him because it was nearly impossible to win the McKenney trophy without his patronage. 

Noted most for his superb match-point play, Crane's systems revolved around opening 4-card heart suits in order to buy as many contracts as possible in 2H, but opening 1Spade required 5 cards. In consequence he was probably an even more ardent exponent of Moysian fits then Alphonse (Sonny) Moyse was. 

It is still possible to find compilations of Crane's bidding system and ruminations on the web.

The post of Grant Baze's memories of Barry., on that final link, are priceless. One oft repeated story is the following:


  Jeff Meckstroth went one better. He played with Barry in a two session
  regional event just because he thought he should play at least once
  with “Mr. McKinney.” At the end of the event Jeff tore their
  convention card into ribbons and threw the pieces at Barry, making it
  very clear that he would never play with Barry again.


Yes, that is the very same Jeff Meckstroth who has had almost as much influence on the bridge world, since Crane's murder, as Crane himself did.

And just for you Tom, because I know you love rulessuch as these:


  But back to the bidding dictums for a moment. Allegedly, among locals
  in SoCal, he[Crane] mandated “Double at match points (for penalty) in
  pass-out seat after an opening 2NT.”
  
  I rather doubt that but maybe others could shed more light.
  
  I have done quick and dirty simulations – finding about 52-55%
  conversion rate. Maybe others can chip in.
  
  Response:
  Ed: I think the statement is correct, but incomplete – after
  “pass out seat”, add “4 hcp's or less”, the rationale being that
  partner holds 11+ hcp behind declarer.