I have just returned from an open tournament (after 9 months of break from tournament play, which is not rare, unfortunately), and in the very 1st round I met a 2500+ GM (the first time in my career in an game for rating)
and tried the Nimzo-Indian for the 4th time in my life. (Yet I had the most experience with that defence vs. 1.d4, due to the few games played and wide variety of defences I had tried...)
And to my surprise, after 20 pairs of moves, as Black in the 6.e3 Sämisch, I was not standing worse, at least.
I screwed it up later on, because this had been the 1st time I got the type of position on the board in front of me and because of the 400+ points of difference in rating, but till then, I was happy that I managed to play these opening moves by heart.
I saw 2 games (annotated here, on chesspublishing.com) two days before the game (starting with 12.exf5 and 13.dxc5), without especially anticipating an opportunity to play it in the near future, and played the moves as far as I was able to remember, while the GM used up a lot of thinking time of his own...only to play the moves I expected.
I made strange mistakes (21....Bxc4 and 22..Bxe2), which I myself was surprised about during the post-mortem analyzis

, but after the first 21 White moves, Black had no difficulties.
Here is the game,
[Date "2010.07.10"]
[Round "1.1"]
[White "Gonda, Laszlo"]
[Black "HoemberChess"]
[Result "1-0"]
[ECO "E29"]
[WhiteElo "2556"]
[BlackElo "2112"]
[PlyCount "67"]
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. e3 c5 5. a3 Bxc3+ 6. bxc3 Nc6 7. Bd3 O-O 8.
Ne2 b6 9. e4 Ne8 10. O-O Ba6 11. f4 f5 12. exf5 exf5 13. dxc5 bxc5 14. Ng3 g6
15. Be3 Qa5 16. Be2 Rf7 17. Qd5 Nc7 18. Qxc5 Ne6 19. Qxa5 Nxa5 20. Bf3 Rc8 21.
Bxa7 Bxc4 22. Be2 Bxe2 23. Nxe2 Nb3 24. Ra2 d6 25. Bf2 Rc4 26. Rb1 Nbc5 27. Rb4
Re4 28. a4 Re7 29. Rxe4 Nxe4 30. Bb6 N4c5 31. a5 Nc7 32. g3 N7a6 33. Kf1 Nd3
34. Rd2 1-0