I'm a tools junkie! Anything that helps be work more efficiently is HUGE for me since every 10 minutes I can "save" in a day is 10 minutes with my Children, talking to my Wife, on my Harley, in the gym, etc.....
I've been a Visual SlickEdit user for many years, you can set it up to look/work like Visual Studio and it has syntax highlighting for EVERYTHING (even stuff I've never heard of) and there are versions for Windows, Mac OSX, Linux, Solaris, AIX, HP-UX, etc.
Now they've come out with 2 tools add-ins for Visual Studio.
Each is priced at $49
You can read full feature lists here.
The versioning stuff is interesting but for me the Editing Toolbox ROCKS.
Here are the highlights from their site - download the trial, if you decide to keep it, it's only %40
Aliases and Acronyms: Use directory aliases to save keystrokes and mouse usage when opening files. Use acronym expansion to save keystrokes when typing class, namespace, or function names in your code. Auto Code Doc Viewer Extract header comments into MSDN-like documentation, fully linked HTML help that can be browsed in Visual Studio as a tool window and exported for sharing with others. Code Annotations Insert comments and notes about code without actually modifying the source file. Comment Wrapping Enable automatic wrapping of any type of multi-line comment as you type. You can also reflow existing comments in the current file. Icon Extractor Simplify the task of finding quality icons and applying them to your applications. Quick Profiling Fine-tune your profiling to get information about a specific section of code. This feature allows you to time many cases that are not possible with standard profilers, such as timing complex loops, recursive functions, and the time between an object’s creation and disposal. Regex Evaluator ( *** a must FOR all web developers) Interactively create and test regular expressions, which are used to express text patterns for searching. Code Navigation Use keyboard shortcuts to jump from a symbol to its definition and to list all references for the current symbol. Word Completion Use commands to search for and insert additional text from a matching string.