To get the special items in the game, you need dog tags. Here is a list of how many you need for each item:
Tanker
Bandana - 30% of all dog tags or 46 dog tags(infinite bullets)
Stealth - 50% of all dog tags or 78 dog tags(invisible to enemies but bosses)

Plant
SP wig - 30% of all dog tags or 73 dog tags.(infinite bullets
stealth - 50% of all dog tags or 121 dog tags.(invisible to enemies but bosses)
Wig B - 70 % of all dog tags or 170 dog tags.(infinite grip guage)
Wig A - 90 % of all dog tags or 218 dog tags.(infinite O2 guage)

To get the special items, you must complete the episode in question and save after all the movies/credits. When you load the game for the next game, you can pick either the tanker or plant and you'll get the items you gained.

I trust you all know how to get dog tags, but if you don't, then read this. When a guard has his back turned to you, go up to him with a hand-gun and press fire but keep it held. Then, when the guards arms fling up into the air, walk to his front with your gun still pointing at him. Aim the gun at his face to get a dog tag. If the guard says something like "who are you" or "just try to pull the trigger", then shoot him in the arm or leg with your Socom/USP.

All guards have dog tags on the difficulty levels very easy, easy, normal, hard and extreme excepet the guards who are called in for back-up.