Resharper (and now all the various Jetbrains tools) - from the early days, this tool allowed you to aggressively and automatically refactor code. Before that, i

Resharper (and now all the various Jetbrains tools) - from the early days, this tool allowed you to aggressively and automatically refactor code. Before that, in the C# world ( and many other languages ), there was very little in the way of automatic refactoring tools. Not to mention it's automatic suggestions on code transformations or more efficient use of the language are super useful. Vim Bindings - While I often don't use Vim, I use Vim binding in most any environment I use. I don't know if it really made me a better programmer, but it improves the experience of programming. Unit Testing tools - making code testable makes code modular. Visual Studios Debugger, fantastic debugging tool from years and years ago. While I don't use it as much anymore, it's been a useful tool in understanding code. Google Search, transformed the way to get information, coding information was hard to come by a few decades ago, now it is prolific.