Tool Box

Since I've seen many projects and therefore worked with lots of different tools, I put together a list of stuff I appreciate.

Unity3D, the cross platform 3D/2D engine for games and apps of my choice.
Git, to not lose any code and make work in teams easy.
Visual Studio, my IDE for C# and JavaScript projects. It's kind of a beast, but has all the functionality you need in one place.
ReSharper, for faster coding in C# and consistent coding style. The one plugin I use for Visual Studio which makes coding (and refactoring) really fun.
Jira, to work agile in a bigger team. Even works for small teams. It is web-based (a good idea is to host it directly at Altassian to not worry about updates), so no need for an installation on each client. Became much better in matters of response time, so the disadvantage to a desktop client became less and less a problem.
Confluence, a central place for ideas, designs and other documents of a project. You just don't want to mess with Word documents on documentation heavy projects.
Jenkins, because you don't want to deploy your project every day (or more). From a certain team size you'll need regular versions of your project (continuous development). So setting up a build server once to take that work saves you a lot of time. Jenkins is open source, free and well tested.
Hansoft, another project management tool that worked out nicely in some of my projects. The only downside is that it is client-based instead of web-based. But this has also the advantage of a faster UI response time.