Aaron Bertrand has a compendium of bad habits, anti-patterns, and Festivus-quality grievances to air:
Going back more than a decade, I’ve been writing and presenting about what I call “bad habits” – typically shortcuts or sub-optimal ways to do things in SQL Server. Often users just don’t realize these things are bad or that there is a better way.
Here is an ongoing list of articles that I consider to be along these lines – eradicating bad habits or at least promoting best practices. Not all are explicitly framed as a “bad habit,” but they do all present things I wish I observed less often.
Click through for a disturbingly long list of items.