Greenshot provides a really convenient and effective way to capture screenshots in addition to editing them.
No install required just download, unzip, and execute greenshot.exe. It supports three types of screen captures; region, window, and full screen. Images can be saved as JPEG, GIF, PNG, and BMP. The screen shot can automatically save as a file, sent to a printer, clipboard, or image editor. The image editor supports drawing rectangle, ellipse, line, arrow, and add text. This screen capture tool is easy to use and can allows you to quickly add ellipses, rectangles, lines, and arrows to the image.
Activate region mode by hitting the Print key on your keyboard or by choosing Capture region from the context menu. Left-
Activate window mode by hitting Alt + Print on your keyboard or by choosing Capture window from the context menu. Click the window you want to be shot. After clicking, the image editor window will open for further editing of your screenshot.
If you want to shoot the complete screen, just press Ctrl + Print on your keyboard or choose Capture full screen from the context menu.
The complete screen will be shot instantly, the image editor window will open for further editing of your screenshot.
More features on the official Greenshot site