No one's going to say he's the sharpest knife in the drawer.

Sam Adam, Jr., arguing to the jury in United States v. Rod Blagojevich.

Alternative phrasings:

Not the brightest light on the porch.

One beer short of a six-pack.

Two bricks shy of a load.

A few fries short of a Happy Meal.

One twist short of a slinky.

The gates are down, and the lights are flashing, but the train isn't coming.