The snip/snipping tool is only a convenience tool.
Everything that it does can already be done either using the standard Windows Paint or use GIMP,
and GIMP does a lot more.
http://windows.microsoft.com/en-US/windows-vista/Use-Snipping-Tool-to-capture-screen-shots
Free-form Snip: The Windows Paint > Free Select Tool (looks like a Starfish)
does this. Then Right-Click the area that you surrounded > choose Copy.
Then Paste. You might want to resize a File > New canvas to smaller than the copy size before Pasting. Windows Paint is at Start > All Programs > Accessories > Paint, or should be.
Use the GIMP
Free Select Tool. Looks like a Lasso.
Click around the part of the picture that you want to snip.
Complete the snip by clicking around the part that you want and then when you get back to the first dot, then click on it to complete the snip. An edit box will form around the area and you can Right-Click on it and Edit > Copy the area. Then Right-Click > choose Edit > Paste, or, in an area that you have previously circled with one of the Edit Select boxes, you can also use Paste Into (the selected area).
Rectangular Snip: Use the Windows Paint Select Tool (Rectangle) to surround an area of a picture that you have opened in Windows Paint.
Left-Click and Drag the Mouse Cursor to do so. Then Right-Click the area that you have surrounded and choose Copy. Then click File > New.
A blank canvas appears. Resize it to smaller than your copy image by dragging the center borders where the dots are. The cursor will change to two-way arrows when you are on the right spots.
Then Paste the Copy. Making the canvas smaller is so that the Copy is not surrounded by empty canvas.
In GIMP do the same with the Rectangular Selection Tool, but instead of resizing the canvas, in GIMP Right-Click > choose Edit > Paste as > New Image.
Window Snip: This is used to take a screenshot of a specific window instead of copying the entire desktop screen. They call it the window that has the Focus. It is the window on top that is in use.
Press and Hold the ALT key while pressing the Print Screen key.
Then in Paint click Edit > Paste. You might want to resize the canvas smaller before Pasting the copy.
In GIMP, after taking the ALT-Print Screen screenshot,
click File > Create > From Clipboard.
The Clipboard is a system function and it stores anything that you copy, text or screenshot. GIMP also has a File > Create > Screenshot that might also be useful.
Full-screen Snip: Press the Print Screen key. Do not press the ALT key when you do. Then Paste or Create > From Clipboard.
GIMP also has extra snip tools which use shape of area, and others use the color of an area to surround it. You can Right-Click on an area > choose Select > By Color.
The Mouse Cursor changes to a Color Selector Tool. Click on the area by color to outline it as an edit area, then Right-Click and Edit > Copy (or do whatever you want to do with the area, add lights, add a gradient, etc.
In GIMP you will want to check the Toolbox controls for each tool like Select Color and, if it's there, set the Threshold to 0 (Zero), else you will get a rough outline in the copy paste. The higher the Threshold number, the rougher. You might also want to turn off any GIMP Antialiasing controls for a tool, if there, for the same reason.