@hamish you`d be surprised lots of types of wires :p
since you love challenges, how about make a particle engine, like sparks,fire,dust(can trail off roll objects)and any other things
and the sparks could fly off the hanging wires that are apparently so easy to model
you could also have gas canisters/fire extinguishers and when shot they spray out lots of transparent plains and there x,y,z values rapidly increace, and you could add a force of them so they start flying about everywhere.
this could be done with wires aswell everytime it makes a spawk it randomly swings in some direction.
you could also simulate picking up objects, using the newton mouse drag thing thats in some examples, but you wouldent be able to pick up heavy objects or maybe with dificulty, and the range of the selectable objects wouldent be very far, with this you could be able to move manhole covers, open doors nice and slowly :p.
well if you do get around to adding ai you could make moving the objects by hand make less/no noise compared to walking into them or planting a nuke so nearby enemys dont become alerted.