TLDR: In China, after failing to legally check 2 souvineer knives in our luggage, I got detained for accidentally missing a key ring multi tool in my cary on.
Story Time:
We were in China on a trip for my work, and part of what I was doing was running sports camps for kids. I had some basic medical supplies- including an infantecimally small Gerber multi tool (kind that goes on your key ring). Got burried in the bottom of my carry on- and I checked that thing THOROUGHLY, somehow missed it.
One other guy and I had bought some decorative looking knives, and put them in our check bags. We studied the regs very carefully, and checked the giant red sign which explained this exact issue in English, and confirmed with an airline rep. My buddy checked his bag, no problem. Then it was my turn. They opened my check bag, saw the 6" fixed blade knife with a sheath (probably cheap tourist crap anyway), and flipped out. Called me behind the counter, and we argued back and forth about wether it was allowed. Mind you, this is CHECKED, and the blade clearly fit well within the descriptions of allowed checked items (which specifically addressed blades). They summoned the police, at which point I threw up my hands and told them to keep it. Maybe the agent was the knife sellers cousin, and this a racket.
We are in the Chinese TSA line- and a cop comes up and pulls our whole group out of line, then separates my friend and I, and we get escorted back to the check counter. They went and dug up all of our bags, and found his knife. They are MAD thinking we are smuggling things. We tell them to keep it, get our butts chewed out in Chinese, and are sent on our way. 3 cops are now following us all the time.
I am really ticked off, but just ready to get home. I am last in line to go through Chinese TSA, when the machine beeps on my bag. The agent opens it, and produces the "knife" which is little more than the pointy end of finger nail clippers for cutting gauze. I am mortified, and apologize, trying to explain. he says "YOU CANNOT TAKE!". I say I'm sorry, please throw it away, It is medical supplies.
He stands up and starts saying something very loudly, and a rather alarmed guy (stranger) behind me says "He is saying you have a knife!". The rest of my group is through security. The cops run at me, clearing everyone away, and I am detained and taken to a very small room at the end of a dark hallway. I wait 10 or so minutes alone, thinking "This is how I disappear. I'll never see my family again."
I explain the situation, they are not happy. I am threatened when 5-10 years in jail, accused of terrorism and spying (they were rather paranoid). Everything I brought with me is laid on the table and searched down to the stichcing. They make me open files and folders on my computer. Thank God I brought a clean laptop. I have to recount to them every single day of my trip, where I went, who I talked to, what I did, where I stayed (which they are comparing with our registered itenaraity).
I tell them I just want to go him to see my newborn son (who was 2 weeks old when I left). They question me, so I get my phone and show pictures. Finally convinced I am not a spy or terrorist, they give me a lecture about American arrogance and Chinese superiority, and send me on my way. All this is during the Beijing Olympics, so might explain some of it. We're were on the other side of China, though.