Is the player stupid or the character? I'm a good player, but I'll do stupid things if they're in character. I had a barbarian who decided he was sick of listening to the rest of the party debate...I thought to myself "W.W.C.D.?" (What Would Conan Do?)
"Enough talk!"

charged the Druergar...lost badly....and managed to get most of the party sold into slavery to the Drow.

But...then there was James, who, until he played in my Shadowrun game, was nicknamed "Dead in 60 Seconds" because he would do things like wander into rooms before the thief even got there, and since he liked mages....

Yeah.

"James, what have we told you about grenades?!
It wasnt me this time! It was the bots!"
-James doesnt play well with others, CounterStrike