Know everything there is to know about Design Patterns?  Well it is time to move on to Anti-Patterns.

Anti-Pattern: An AntiPattern is a pattern that tells how to go from a problem to a bad solution. (Contrast to an AmeliorationPattern, which is a pattern that tells how to go from a bad solution to a good solution.)  A good AntiPattern also tells you why the bad solution looks attractive (e.g. it actually works in some narrow context), why it turns out to be bad, and what positive patterns are applicable in its stead.

Some Favorites:

For the whole list, http://c2.com/cgi/wiki?AntiPatternsCatalog is a good starting point.