Ubuntu comes with a "Take Screenshot" function in the Accessories.
It looks good as you can grab the whole desktop, current active window or a fixed area, with a time delay setting. Effects to include pointer or window border or drop shadow.
All looks good, except that when I choose an active window, the screenshot doesn't include the window frame.
After some research,
chewearn's blog says this problem was reported two years ago (or nearly three years counting from the new version 9.10 now). Still not fixed by Ubuntu.
And he can come out with his own script to get it solved. I've not tried the script yet.
Any other better choice?