I was going to say 'use whatever means necessary, smash their faces in, pull their teeth out, fuck the geneva convention, torture the basterd... in a war situation anyway' and I kind of think that sometimes if I am being honest.
But after taking a step back and thinking about it I remembered something, something very prominent in the U.K, November 5th. Bonfires and fireworks and shit in rememberance of 'The Gunpowder Plot' when a man named Guy Fawkes or Guido Fawkes allegedly tried to blow up the houses of parliament.
Check out his signature both before -

And after torture -

I researched this years ago as part of a school history project and it still leads me to think that a man would sign anything after being tortured and if he didn't then it was more than likely because, he was dead.
Now just to make some comments on some of the initial points.
Prolonged isolation - Not torture in my mind, some people like it.
Prolonged sleep deprivation - One of the ultimate and worst forms of mental torture known to Ric

Sensory deprivation - jedi training
Extremely painful "stress positions" - ouch... torture, the same as beating someone up
Sensory bombardment (such as prolonged loud noise and/or bright lights) - sounds like a nightclub not torture

(torture really!)
Forced nakedness - can be embarassing but you can always embrace it

not torture
Sexual humiliation - what you mean rape and shit? Torture man.
Cultural humiliation (such as desecration of holy scriptures) - not torture, take it like a man, you are in prison.
Being subjected to extreme cold that induces hypothermia - torture
Exploitation of phobias - not torture, some people do this to overcome their phobias, it's just mean, funny if you do it to someone though. Go on go and get a spider and take it to your mum

Simulation of the experience of drowning, i.e., waterboarding. - torture
In conclusion I dont know really, it depends what one considers torture. And in which situations it should be used but then as I said, is torture the best way or will a man succumb to anything after torture?
What are yout thoughts on using Sodium Penthanol (Truth Serum) and a lie detector, even at the same time?
EDIT: We all know the CIA are, to coin the phrase, 'as bent as a nine bob note anyway' (i.e a £9 or $9 note) so of course they have broken human rights treaties etc as I am sure many other organisations across the globe have done.