Lets see...

I have a Nalgene that I travel with all of the time. It is usually half-full, but I once took it through full! Not even a peep from the screener....

I work in an IT Department, so when I travel, I have a few screw-drivers in my bag. They are easily more than four inches. Have not had problems with these being taken or questioned...

One time a year or two ago, I was at a shooting range... Unknown to me, I left a few bullets in my jacket pocket, which was run through the x-ray... Not a yap from TSA..

I suppose most of the stuff I travel with is considered dangerous... I could remove the battery from my laptop and hit people with it... I could stab people with my pen. I could also strangle or tie-up people with my laptop charger...