Thus far, I have mainly been an embedded developer, but I am interested in having the flexibility to do mobile and web development as well. I think my tools should include the following, but probably a lot more.
LAMP stack.
Java IDEs like Eclipse and IntelliJ.
JS frameworks like Dojo, Node.JS, AngularJS, (is it better to mix or commit to one?).
Cloud solutions like EC2 and Azure (again, ok to mix or better to commit to one?).
Google APIs.
Continuous integration server.
Source control tools with Git for new work, SVN, CVS, +others for imports.
FTP server.
Unit test runners.
Bug trackers.
OOAD modeling tools or plug-ins?
Graphic design tools?
Hosting services.
XML / JSON / other markup?
Content management, SEO?
I am also interested to know if there are tools where it might be better to mix, match, or support all available (maybe for source control) and others where the full focus should be on one (maybe Java vs. C# or Windows vs. Linux vs. MacOS). Perhaps some of these questions need context of whether the projects will be greenfield (just pick favorite) or maintenance (no choice, each project continues legacy, sometimes with a poor tools).