3. Loki Thinking He Could Lift Mjolnir - (Thor)
After having just lied to Thor about their father dying and after having put together a dastardly scheme to usurp the Asgardian throne, what on Earth made Loki think that he had a chance of lifting Mjolnir? In the makeshift S.H.I.E.L.D facility built around the hammer's landing spot in New Mexico, Loki arrived (appearing to be wearing Earth clothes) and appeared before Thor to lie to him about the death of their father. He then headed to where Mjolnir was rooted to the desert floor and, with S.H.I.E.L.D agents crawling everywhere around him, attempted to lift it and looked incredibly frustrated when he couldn't do so. Why would he assume that there was even a remote chance that he could, given the requirements of being "worthy"? Very, very dumb.