- Return to the days of mixed-case menus
- Edit colors and themes
- Productivity Power Tools
- Use WinMerge as the Compare tool for TFS
- Slow Cheetah XML Transforms
- Microsoft Visual Studio Team Foundation Server 2012 Power Tools
- Git Extensions - I find myself increasingly using Git as a local repository for spike code so that I can avoid the ceremony and overkill of TFS Source Control
- SQL Server Data Tools - really handy to have installed when you want to merely run a query or examine a database
Entity Framework Power Tools are worth evaluating. I haven't spent very much time with them yet, but generating a diagram from a DbContext is useful.
LINQPad isn't an extension, but is indispensable if you work with LINQ. I want to also call your attention to this excellent post on calling SQL Server stored procedures from LINQPad. I never thought that I would ever need to manipulate the results of a stored procedure call in LINQPad until today, and fortunately BillKrat's article showed me the way.
Though not part of Visual Studio, Team Foundation Server Integration Tools is incredibly useful if you need to selectively migrate portions of a project, such as Work Items only. Using the tool requires at least an intermediate level of knowledge of TFS.