NHL 12

this ones pretty simple. you'll play the 2011 winter classic when you start up the game for the first time. all you have to do is complete that game and you'll get the achievement, regardless of the score.

NOTE: you dont have to get this achievement at the very beginning of the game, it can be done at any time. all you have to do is go to game modes, then select winter classic, make sure that your playing as the PENGUINS, at home, against the capitals. complete the game and you'll get the achievement, doesn't matter what the score is

That one is pretty simple. You just have to play the 2011 Winter Classic to get this achievement.
The only important thing is, that you DO NOT play with different teams. Play the original 2011 Winter Classic. It doesn't matter if you choose Pittsburgh or Washington. After the match ends the achievement should pop up.

I just got it by playing with Washington on Pro Difficulty with 4mins Period Lenght. I won the match 3-2.