sisyphean = endlessly laborious and futile (from Sisyphus)

Attempting to index all the blogs on the Internet would be a sisyphean job.

tantalize = to torment by keeping something desirable just out of reach (from Tantalus)

Arranging the display of lovely, expensive jewelry would tantalize Maria every time.

halcyon = calm, peaceful, joyful

In the workplace, we often yearn for the halcyon days of college.

argus = watchful guardian

The argus eyed Secret Service agents protect the President.