I'll add a few to the mix:

*Creative uses of CASE, since there's no if structure except in procedures, functions

*Know how to create a user defined function and when it is useful or needed

*SubQuerying in the Select, From/Join, and Where clauses

*Handling multiple instances of the same table in a single query

And knowing that there are other databases and SQL variations out there and how they differ to what you have available in tSQL.