There are a lot of things you carry on your person that are potential weapons, so not sure where you were going with that.
A chain for a bike lock system is very handy, tough to cut, except with an angle grinder, and will conform to whatever object you put the chain around.
If you're bike is expensive, you should be considering an angle grinder resistant lock, battery powered angle grinders have become all the rage among pro bike thieves. Locks like the LiteLok X3; Hiplock D1000; Squire Stronghold D16 Max; Abus Granit Super Extreme 2500, this lock is the heaviest of the lot and probably the toughest to cut; Skunklock Carbon, this lock will not hold up as long as the first four will against an angle grinder, but it will release a poignant odor! All of those locks will take between 3 to 5 disks to cut through, and between 2 to 4 batteries.
Another lock is the Altor SAF, this lock is actually angle grinder proof, but one look at the size of that thing is enough to want to leave it at home!
But if you have a nice bike, none of those locks will prevent someone from stealing your components. So the best method of protecting a high-end bike is to leave it at home and ride a $250 or so used bike to places that you need to lock up the bike, then just buy a cheap $40 or so lock, and use the good bike for when you're not going to leave it someplace.