For crisp clean graphics, and fluid animation, give Blender a try.
Great for making smoke poofs and fire animations. The fluid and physics simulator make so you can do some neat special effect's.
You can even set the materials to non-shaded to give a flat-solid-lifeless look like things from inkscape.
Another great tool for game design is Neo-Texture-Edit. It generates 100%seamless tiles. Great for game tiles!
Make humnan is another cool resource, you can make a human to your specs, pose and animate them in blender!
Anyway, go to sourceforge and poke around, you will find all kinds of great liitle tools and utilitys.
Imagemagick is a commandline tool for images, you can make scripts to re-size entire folders of images. Neat for batch prossessing and compositing.
FFMPEG- will let you convert and tweak any video and audio files.
SWF tools will let you make small SWF files from a veriety of image sources.
Wings 3D is a solid modeler that will produce 100% watertight models for animating or 3D printing.
Sculptris- A killer application from Pixologic! Sculpt with millions of polys! Neat for faces, and making tree stumps!.
Texturemaker- Like neotextureedit, only $70 more expensive... THey have a lot more tools than Neo like a particle engine and a few ways to geerate random textures.
GenTex- If you are wealthy, and have $200-$5000 to spend on applications Genetica litterally has a "Make me a cool texture" button. Very overpriced, but very impressive!