I'm bracing myself for lots of "NO YOU'RE WRONG. IT WAS _____" in the comments, so if you're reading this, consider this an audience participation thing. This is just my lowly opinion. Heck, maybe other writers'll chime in and make this a fancy-schmantzy storystream of their own personal top Blues moments. Who knows?
For me, personally, the top moment was the end result of an organizational move that I questioned very much when it first happened. In my opinion, the top moment was the Central Division Championship, and it was the end result of the hiring of Ken Hitchcock as coach. I couldn't say the best moment of 2012 was Hitch's hiring considering that happened in 2011, but I can include a good chunk of the positivity that happened afterwards.
Who legitimately thought, at the start of last season, that the Blues would be competing for the Presidents Trophy the last few weeks of the year? If it weren't for the way that they backed into the playoffs, they would have won it. Instead, fans just had to settle for the team with the second most points in the Western Conference, and a team that convincingly won the Central Division for the Blues for the first time since 2000. How the Blues got to the point that they did during the regular season was attributable by a large amount to Hitchcock. Smart defensive planning took some of the top young defensemen in the game and turned them into what was tantamount to a brick wall. Further reinforcements in the wall area came from Jaroslav Halak, who completely turned his play around after Hitchcock's system was introduced, and from Brian Elliott, who had a career renaissance. The Blues allowed a paltry 1.89 goals a game. The team behind them, the eventual Stanley Cup Champion LA Kings, allowed 2.07.
Did the Blues have a break-away goal scorer? Not really, though one could make the argument that had David Perron not missed 30 games he would have broken 30 goals. This was winning by committee, with a large responsibility placed on the team's strengths -- defense and goaltending. Hitchcock showed the team how to get the most out of their strong points, and by doing so allowed the team to rack up an impressive 49 wins.
The team isn't built for amazing flashes of offense. This team is built to wear opponents down and to stymie their every goal-scoring chance. Davis Payne wasn't getting that out of them. Ken HItchcock did. Perhaps if this lockout'd end at some point in the near future, we could judge a bit better long-term what the hiring of a new coach has done for the Blues. As it stands, we're just going to have to admit that it's the best thing that's happened to the team in a long time, and that eventual banner raising will be proof that his system works in St. Louis.