This updated version of Snag-it appears to be somewhat similar to Greenshot, though Greenshot does not do irregular shape selection or video recording. However, Greenshot is free.

Greenshot also has the flexibility once you have captured the image - you can add transparent highlighting, text notes, and various shapes, all of which can be manipulated after placement. The only "inconvenience" with it is that you have to copy your finished shot to the clipboard before you can save or paste it into its final destination. However, if you want to simply grab a screenshot without manipulating it, you can set a preference to copy it directly to the clipboard and bypass the extra editing, much like Snag-it 10.

What can I say? I like freebies.