It would be nice if you include Greenshot.

Greenshot is a very tiny tool to take screenshots.
It is similar to PicPick but it is only around 600 kb.

Description

Revolutionary screenshot tool optimized for productivity. Save a screenshot or a part of the screen to a file within a second. Apply text and shapes to the screenshot. Offers capture of window, region or full screenshot. Supports several image formats.

My Opinion
A very tiny tool to get the task done. It has a built in image editor to apply text and shapes.
Neat tool.

It is portable and open source.
Website: http://greenshot.sourceforge.net/
Download: http://sourceforge.net/projects/greenshot/files/

Setting in C:\Users\XXX\AppData\Roaming\Greenshot\config.dat