ATITool is an overclocking utility designed for ATI video cards. Design target is to write a light-weight application for the enthusiast

ATITool Features
No limits overclocking.
Finding maximum core and memory overclock by rendering into a Direct3D window and scanning the output for visual artifacts.
Temperature monitoring and fan speed control (on supported cards)
Removal of Catalyst overclocking lock for 9000/9200/9550/9600 series.
Artifact scanning mode for non-ATI cards - use together with a 3rd party overclocking utility.
Loading a predefined clock profile on Application/Windows startup.
Hotkeys that can be used any time to load clocks from a profile.
3D application detection (Direct3D 8, Direct3D 9, OpenGL) to overclock your video card only when required.
Gamma control