Look at shutter, the feature rich screenshot tool. In Microsoft App terms, it is actually a combination of the snipping tool and ms paint.
It captures screenshots, but it also has an edit mode for the screenshots (or some file you can load from your hard drive) with some basic drawing tools, which are well thought-out and quite usable for inserting arrows and numbers into images, cropping, etc. Things you do to images to cut +paste them into presentations, after editing.
Update 2021: These days, I would install Shutter from Snapcraft