Though I assume you have already long since made your decision on this, I would like to point out the catch in turning your opponents sword into a Slinky and that is that you must have "possession" of it first.
Stated in the SRD : A spell’s components are what you must do or possess to cast it.
And stated in fabricate the materials to be transformed ARE the material components for the spell.
I would allow a player with "acceptable proximity" to an unattended material to be considered in possession of it...but it if it is connected to someone else and in no way connected to the caster...then I would not.
It is my understanding that the range given in Fabricate indicates where the resulting "product" can be generated. So you could "posses" a wooden wall that is next to you and fabricate another wooden wall (or whatever you want it to be) anywhere in range.
You can recontextualize this with other spells if it helps:
I would not let someone with no food cast animal messenger because he is in "close range" of a restaurant or the targeted animal is actively eating in close range.
I also would not let someone cast Flaming Arrow because someone else had oil and flint in close range.
Now...I have had lots of discussion about this and the idea of using contested possession as a material component is generally a cool enough trick that we let it slide. Since the material component destruction has no rules though it can get kind of harry...(Does immunity to spells prevent the use of something as a component?) Heroics' MC is a piece of equipment used by at least a 15th level fighter in battle (and note...it does not say anything about it not being magical)....If a mage wants to touch the +5 vorpal sword the 15 level fighter is using and cast Heroics with it to destroy the sword by taking a chunk out of it...well, go ahead and let him...But now you got a Wizard in touch range of a REALLY pissed off fighter. In the same vein I would totally allow a mage to fabricate anything matching the Fabricates target as long as an argument for possession could be established.
In this case...he could: Destroy equipment, vehicles, doors, walls, floors, corpses, traps, spellbooks, cloths, ropes, ladders, stairs, famous works of art, evidence, instruments, barrels that have stuff in them (and not the stuff that is in them), and anything else unmagical and not alive the he does not want....Perhaps you could reconstitute a tanglefoot bag that was thrown on a friend. I find the best effects are to use it to get rid of a problem and gain an advantage. (Escaping Prison. Friend Chained to a Wall, Fabricate the chain (or the wall its connect to) into a weapon)
In the case of clearly non-possessed Items I would "broaden" the range. If a "fabricator" went into a room and found the enemy's rack of Halberds, I would allow him to sack all the weapons on the rack for the construction of a reinforced blockade. These are all judgement calls of course.
Note also, magical items are out for Fabricate, but enchanted items are in totally different subject...Fabricate can totally get rid of the best arcane lock by just getting rid of the enchanted obstruction