One of the tasks I find to be annoying during development is pasting GUID's into my code. You need GUID's for lots of different functions (COM, Constants, etc ...). GuidGen is a good tool for getting the Guid into your code. However I don't insert GUID's very often. Everytime I do, I find I've forgotten where the tool is. Then I go through the process of locating it and getting my GUID out.
PowerShell to the rescue :)
PS> [Guid]::NewGuid().ToString() | out-clipboard
[Edit1] Corrected ToString->ToString() Tom Barnum's feedback.