Metal Gear Solid 2: Sons of Liberty Message Board  

Requirements:
A gun.
Cant be a Tranquiliser.
(Hard requirements, no?)

The first thing you need to do is hold up an enemy sentry.

Run up behind one and point a gun - preferably the socom/usp - into his back to make him freeze.
Slowly let out square or un-equip then re-equip the gun to cease aiming at him and move infront of him.
(Make sure the gun is equipped when you do so)
Aim at his face or crotch with first-person. (R1)

Slowly let square out again while aiming it to put the gun down without shooting or un-equipping it and move to the soldiers right hip. (Your left)

Shoot his radio. If successful, you will see and hear the sparks fly out of it.
Move back infront of him and shoot his Right raised arm and either one of his legs once.

You can now un-equip your gun infront of him and watch him try and call for back-up..
After that he has nothing to do other than slowly hobble away because his trigger arm is injured.
Do anything you like to him but dont let him hobble away through a door because he tries to.
(It's fun to slap him in first-person view...)

Note:
You may occasionally come across an enemy that has 2 radios, but it's very rare...