This is a list of game development content creation tools that I've used in some capacity while making games. This list is periodically updated.
- Texture Packer is a very good GUI and command line tool to create sprite sheets and texture atlases.
- Sprite Illuminator is a 2D sprite normal map editor for dynamic lighting and special effects.
- Physics Editor is a GUI tool to create collision shapes around 2D sprites.
- Sprite Lamp is a 2D dynamic lighting effects tool making use of hand drawn normal maps.
- Spine is a very good skeletal 2D animation tool with an efficient, streamlined workflow.
- Spriter is another skeletal 2D animation tool using a technique they like to call modular animation.
- Tiled Map Editor is a free, easy to use and flexible tile map editor.
- tIDE is a .NET-based tile editor that allows level designers to easily create content for tile-based games.
- Pyxel Edit is a pixel art editor designed to make it fun and easy to make tilesets, levels and animations.
- Game Character Hub is an art program that is particularly good for game character creation.
- Paint.NET is free image and photo editing software for PCs that run Windows.
- Inkscape is an open-source vector graphics editor.
- Audacity is free, open source, cross-platform software for recording and editing sounds.
- Wavosaur is a free sound editor for editing, processing and recording sounds, wav and mp3 files.
- sfxr is a sound effect generator to provide a simple means of getting basic sound effects into a game.
- Fraps is real-time video capture software for games.