Many of us have done it. Forgotten a water bottle in our carry-on. Didn't take those sewing scissors out of the bag. Or, like me, forgot a brand new bottle of cologne was in my carry on when I left the cruise ship for the airport. That cost me.
But there are lots of other strange things that get noticed in security and an article on Smarter Travel.com lists ten of them. Among them is a boomerang. Now we brought a boomerang home from Australia years ago but in our checked luggage thankfully. I had no idea it was listed as a deadly weapon.
Another one that people tried to get by the airlines was a dead body. Several instances are reported in the article. Like Weekend At Bernie's, they tried to disguise the dead passenger with sunglasses, etc., to make him appear as though sleeping. We have seen that sort of thing done once. On our first cruise to Russia it was reported that one of the excursion buses was late getting started because a family traveling with an elderly gentleman who had a heart attack and passed was "walked" back on to the ship to save all the red tape. Of course we can't be certain that it happened quite that way but it makes a good story.
Beware of those souvenirs. I remember the warnings of taking wooden souvenirs from Papua New Guinea into Australia. All sorts of nasty insects can hide or have eggs buried in the wood. All wooden souvenirs had to be inspected. Thankfully ours passed. Now in the article it is reported that one family was bringing clay objects into the country. When they were inspected it turned out that there were fragments of human bones in the clay. The souvenirs were confiscated as evidence in a murder. Now that's scary!
There are several other items of interest--dead snakes, samurai swords, etc. It's kind of interesting. Can you imagine the book of stories that could be published if all these security people got together and wrote about their experiences?