Tools I use, or am familiar with.

The Gimp
My Image editor of choice, I use Gimp for everything form Photography, texture generation, and pixel art.

Construct Classic
Construct Classic is a great 2d game maker, that exports to DirectX9. There are many plugin that expand an already capable software.

Construct 2
Construct 2 is a new software by the Scirra team. Construct 2 is targeted towards creating html5 web games.

A useful sound generator (when you are going for a classic video game sound)

Unreal Development Kit
I have years of experience from mapping for various Unreal powered games, making the UDK a natural choice for 3D games.

Wings 3D
An easy to use 3D modeling program that is great for props, and decorations.

Other Websites:
Unreal Modders Haven
Ludum Dare
Jest Servers