Sharpshooter is a small application which aids the management of screenshots. When you take a screenshot on Mac OS X with Command-Shift-3 (or with another variation) Sharpshooter will present a window where you can review the picture and choose what to do with it. You can either rename it from its default name to something more descriptive, move the screenshot to the Trash, or cancel the operation keeping the screenshot as it is.
Sharpshooter is a background agent application so you may want to add it as a login item to always have it running in the background. You can control Sharpshooter through the menu status item on the right side of the menu bar.