The Night of the Firebrand - S3-E2
Stupidity: West is introduced to, then knocked unconscious by Vixen as she hides a club behind her back. A trained Secret Service agent like West would not have let his guard down in this situation, as the entire fort was awash in bad guys.
Stupidity: On 8/12/04, Hope specifically told everyone that when the coin was thrown into the force field, there would be a bright flash and that they shouldn't look at the forcefield when this was done. But all three times that the coin was thrown at the force field that day and the next, everyone looked right at it the whole time, and then recoiled in pain at the flash that inevitably occurred.