I had once read an article about people who work in various security-clearance jobs in DC who go to spy and/or espionage movies as a group so they can crack up with each other about "clangers"...elements or concepts that appear in the movie that anyone who works in that sector (or anywhere near it) recognizes as utterly absurd or at least a careless mistake..."Mission Impossible" and "National Treasure" are absolute gems. Or like a palaeontologist who can't help noticing that "Jurassic Park" would be more appropriately named "Mesozoic Park". Or my old roommate at one of my internships who can't watch "House" because the number of jobs the characters do every episode makes her head implode ("They just waltzed right in to the hematology lab!? Gah!!") I know people that will fall on the ground in a verifiable conniption if they hear the phrase "snuck in silently through the ventilation ducts."
The one that I notice most often (I have a MS in health science) is when authors and game systems use the word "prone" to describe someone lying on their back, when they really mean "supine". "Prone" specifically describes someone who is face-down, not merely horizontal. I've also noticed a lot of people (Jim Butcher among them!:O) sometimes confuse the clavicle and scapula. If you don't know which is which, just say collar bone and shoulder blade. That's what lay-terms are for, after all.
I'm curious about other peoples' clangers, partially because they're always amusing, and partially because I know I tend to write fiction willy-nilly about places and jobs I know little-to-nothing about, and I'd love to make fewer avoidable mistakes.:)