[zmd94]

Just try any of the sofwares. It is free:

Aseprite - http://www.aseprite.org (free) A simple animated sprite editor & pixel art tool. This software is completely free to use and is available for Windows Mac. This is a good starting point if you want to make 2D games and draw the characters and blocks for 2D level sprites.

GIMP - http://www.gimp.org/ (free) GIMP is a free image manipulation program. It is good for editing images and performing image based tasks including photo retouching, image composition and image authoring. GIMP works on many operating systems and in many languages.

Inkscape - http://www.inkscape.org (free) Inkscape is a professional vector graphics editor for Windows, Mac OS X and Linux. It is free to use and is good for GUI design and level layout prototyping. You can easily arrange things in the place you want them and quickly draw a concept draft for the visual appearance of your game and GUI.