Way back when I was a juvenile counselor I'd have to fill in on night shifts at a county detention facility. The industrious little deliquents housed there were great at manufacturing improvised weapons and you had to stay on your toes to stay ahead of them.
Looking at the TSA list, a would be deliquent/terrorist could carry on:
1. A toothbrush
2. A cigarette lighter or matches, and
3. a razor blade as long as it is in a cartridge (displosable, etc)
Now the average deliquent/terrorist could take the above items in the lavatory, remove the razor blade from the cartridge (easy to break them open) use the lighter to heat the end of the toothbrush and then insert the back edge of the blade into the soft plastic of the toothbrush. When it cools he or she will have a very nasty cutting weapon that will do far more damage than someone's 1.25" bladed Vitctornox pocket knife, nail clippers, or bottled water.
If I were king of TSA razor blades and lighters or matches of any type would be restricted and I would not be sweating bottled water and fingernail clippers.
I'd have a lot more respect for TSA and the whole security effort if they actually applied some common sense, stopped restricting the harmless stuff as well as the items that would contribute to an incredibily complicated to make or smuggle a bomb plot and instead concentrated on the legitimate threats that they still allow on a daily basis.
I'd probably hire some former juvenile deliquents and see what they could cook up from the list of approved items, then restrict at least one key item essential to whatever they produce.