Unfortunately, although the dev provides a no-install ZIP archive, SnipTool is not natively portable, as it saves its settings to '%LOCALAPPDATA%\Snipping'.
DotNET requirement is v4 according to the homepage.
Sniptool is a screen capture tool that lets you capture one or more selected areas on your desktop and save it with optional annotations. You can combine multiple captures into one canvas and add text, arrows, number bullets and shapes to annotate your capture. There is also an option to blur parts of the image for privacy.
Download SnipTool latest version (currently v1.4) from http://www.reasyze.com/sniptool.