Okay so I spouted off saying I'd gotten all weapons/ items when I happened to notice a spare notch above the fibre wire. Take a peek through a sniper scope and you'll see what looks like a pendant. My guess is that this is the cross, or Rosary beads the Father gives to you when you complete the game- only thing is you leave it behind as you leave in the end sequence. I reckon that if you achieve silent assasin ratibg throughout- you get to keep this and it bestows ungodly powers like inf ammo/ carry all weapons or invincibility (like you really need it)
If anyone else has actually filled this spot then please clue me in.

Hey I never noticed that. Now I have a motivation to get silent assassin on every level. Thanx!

hate to spoil what you guys may think.. but u know u cannot drop the fiber wire.. there is also something else you cannot drop.. you cannot drop your lock pick.. therefor im pretty positive that the missing item is the lock pick i hope im wrong cuz i want that rosery

One thing's for sure, it isn't the lockpick- if you recall on the first level you use the lockpick to open the weapons shed - you then see the fibre wire on the rack. The space above is empty.
My money is still on the crucifix/ rosary- the shape is about right. As to what it does, well remember what Vittorio says about it giving you protection in the closing sequence?!

Any of u guys own the strategy guide? It may say something in there about it.

Nookie.. ur prolly right.. i really wont disagree u prolly have to get silent assasin to unlock it or hopefully there will be codes cuz i beat the game and got every gun now i just want codes to go back and kill everyone for fun.. i looked at it again and it actually does look like a rosery.. so i think Nookie is righ!

Crucifix!!!That missing weapon was a crucifix and it was supposedly used like an anesthetic, but could kill like a wire,but the Eidos guys have taken it out of the game,due to religious reasons,and its effect as a weapon. That's a shame,I'd love to kill someone with a crucifix...