Opposite Extremes:

Mahalo Air in Hawaii:
No security check whatsoever. (This is the friendliest and most amusing airline around; during the safety briefing the FA announced "There are four emergency exits on this plane: two at the front of the cockpit, two at the rear of the cockpit.")

Heathrow to anywhere (especially Athens):
tightest security I've ever seen.

Old Gold is right; security will defeat a stupid criminal, but there is no possible security system that will defeat a bright, resourceful terrorist.

When you consider how many casualties there are on U.S. originating flights as a percentage of passenger miles flown it doesn't make sense for us to waste as much time in security as we already do.