Sword (as well as shields, helmets and armour)
Used In: 300, Troy, Alexander
How Noticeable? The props from Troy were reused for both 300 and Alexander but with so many different designs between them all, you'd have to be a real weapons geek to notice.
Non-descript sci-fi equipment
Used In: Airplane II, Star Trek II: The Wrath Of Khan, The Last Starfighter, V .
How Noticeable? Described by the prop rental company as “dual generators with rotating neon lights inside an acrylic tube; light-controlled panel with knobs and buttons”. It's basically a great big glowing red tube thing and it's hard to miss, but you'd have to be taking a lot of notes to make the connection between films.
Psychokinetic Energy (P.K.E.) Meter
Used In: Ghostbusters, Ghostbusters II, They Live, Suburban Commando .
How Noticeable? Something that iconic? It's like using a lightsaber for a walking stick in a scene and assuming that we wouldn't recognise it.
Used In: The Adventures Of Buckaroo Bonzai Across The 8th Dimension, Star Trek: First Contact and various other Star Trek episodes.
How Noticeable? It would be more noticeable if the rumours that it doubled for Back To The Future 's flux capacitor were true. As it is, it's just a small, grey metal box that has become an in-joke within the Star Trek franchise that only die-hard, fervent Trekkies understand. And we all know how few of those there are.
Used In: Starship Troopers, Planet Of The Apes (2001), Imposter, Firefly
How Noticeable? The armour is pretty easy to spot in Firefly seeing that it was given just a simple spray job, but there's no way to recognise the same helmet used in Planet Of The Apes after the modifications that were made.
Robby the Robot
Used In: Forbidden Planet, The Invisible Boy, Gremlins, Earth Girls Are Easy, The Twilight Zone TV series, Lost In Space TV series
How Noticeable? Unmistakeable. So iconic, he basically set the template for 50s sci-fi robots.
1973 Oldsmobile Delta 88, as owned by Sam Raimi
Used In: The Evil Dead, Evil Dead 2, Army Of Darkness, Spider-Man, Drag Me To Hell, Crimewave, Darkman, A Simple Plan, The Gift, Evil Dead (2013)
How Noticeable? Not only noticeable but a welcome cameo to actively look out for in any Sam Raimi film. Shame he couldn't find some way to have it parked up in the Emerald City in Oz The Great And Powerful though.
Used In: No Country For Old Men, The Texas Chainsaw Massacre (2003), A Murder Of Crows (as well as Married With Children, Modern Family, Desperate Housewives, Scrubs, Everybody Hates Chris, Angel, Louie ... the list goes on).
How Noticeable? Once you are aware of this prop's existence, it's almost impossible to miss that woman's headshot on the printed page. She really deserves her own IMDB page.
Licence plate 2GAT123
Used In: L.A. Story, Beverly Hills Cop II, K-9, Eve of Destruction, When a Man Loves a Woman, Go, Pay It Forward, The Perfect Nanny, Traffic, Mulholland Drive, Training Day, Be Cool, Harsh Times, Kiss Kiss Bang Bang, Role Models, New Girl, Curb Your Enthusiasm and many more.
How Noticeable? Who ever takes notice of something as innocuous as a random bunch of letters and numbers on the front of every vehicle on screen? And yet, once you know about this frequently used combination, it'll be as easy to spot as those fake 555 phone numbers.
USAF AN/FSQ-7 (SAGE) computer system
Used In: Independence Day, Everything You Always Wanted To Know About Sex But Were Afraid to Ask, Sleeper, Westworld, U.S. Marshalls, Gremlins II, Beverley Hills Cop III, Jay And Silent Bob Strikes Back, Austin Powers In Goldmember, Lost ... and so, so many more.
How Noticeable? At the time the computer was first built, it was the largest in the world so it used to have a big impact on screen. Nowadays though, great big old-fashioned blinking computers have become so commonplace in computer-lab scenes that they just blend in with the background.