A hilarious one I got from santabanta.com

Military Performance Appraisals:

Not the sharpest knife in the drawer.
Got into the gene pool while the lifeguard was not watching.
A room temperature IQ.
Got a full 6-pack, but lacks the plastic thingy to hold it all together.
A gross ignoramus -- 144 times worse than an ordinary ignoramus.
A photographic memory but with the lens cover glued on.
A prime candidate for natural deselection.
Bright as Alaska in December.
One-celled organisms outscore him in IQ tests.
Donated his body to science before he was done using it.
Fell out of the family tree.
Gates are down, the lights are flashing, but the train is not coming.
Has two brains; one is lost and the other is out looking for it.
He`s so dense, light bends around him.
If brains were taxed, he`d get a rebate.
If he were any more stupid, he`d have to be watered twice a week.
If you give him a penny for his thoughts, you`d get change.
If you stand close enough to him, you can hear the ocean.
It`s hard to believe that he beat out 1,000,000 other sperms.
Some drink from the fountain of knowledge; he only gargled.
Takes him 1-1/2 hours to watch 60 minutes.
Wheel is turning, but the hamster is dead.