Many of the most iconic pieces of movie memorabilia have turned up at auction, but several are still elusive, and some are lost forever.

Here are 10 we would love to see cross the block...

10. Costumes - Star Trek: The Next Generation

This rifle was sold for $231,000, but many other props from the series will never be seen

Star Trek: The Next Generation is known for its legions of dedicated fans or "trekkies", some of whom would stop at nothing to own an original prop or costume from the series.

One particularly obsessed fan, Kevin Buehler, was arrested in 1990 for stealing a host of props from Paramount Studios, where the show was filmed, with items including Captain Kirk's uniform and a Klingon mask.

Around 70 of the items were recovered, but many still remain missing, with Buehler supposed to have sold them on at a considerable profit. In all, more than $150,000-worth of iconic props are still out there.

Buehler received eight months in prison.

In April, William Shatner's laser rifle from the original Star Trek sold for $231,000 through Julien's Auctions.

9. Maria robot - Metropolis (1927)

This stunning replica sold complete with a toy monkey that was formerly owned and loved by Fritz Lang and given to 'Forry' personally

Fritz Lang's Metropolis was a landmark in movie history. The first feature length science fiction movie, it was also the most expensive film ever released at the time.

With the film made in 1927, very few of the original props have survived. So coveted is any item from the original film, that even the movie's striking artwork is hailed as "the crown jewel of the poster world" and held the $690,000 record for any movie poster sold at auction.

It goes without saying then that the original "Maria" Robotrix costume worn by Brigitte Helm in the movie would sell for a huge sum if it ever appeared, but sadly, it was destroyed in a fire shortly after filming.

If Maria is a must-have for your collection, you can buy replicas at auction, with one owned by legendary science fiction collector Forrest J Ackerman, also known as Forry, appearing with an $8,000-12,000 estimate at Profiles in History in May 2009.

8. Mary Poppins' umbrella - Mary Poppins (1964)

Thanks to the Broadway musical, the market it awash with replicas

Who can forget Mary first drifting into view during Disney's much-loved 1964 classic? Her parrot-headed umbrella is an iconic object from many of our childhoods, but what happened to the beloved brolly?

Well, the answer is that we just don't know. However, you can still own the famous carpet bag that Mary carried around with her. In fact, it last appeared at Profiles in History in June 2010, holding a $10,000-12,000 estimate.

7. Mini cars - Italian Job (1969)

The chase scene in The Italian Job is one of the most famous ever made. Ask any petrolhead about it, and they will be able to paint you a vivid portrait.

Though three Mini Cooper Ss appeared on screen, there were actually a total of 16 used for filming, all of which were scrapped in Italy once the film had been released.

Thankfully, a dedicated collector bought three of those and, enlisting the help of Michael Caine and the film's chief stunt driver, Remy Julienne, has restored each one back to its film specifications.

They have been put on display in the UK, but it seems unlikely that their owner will ever want to part with them.

6. Chopper motorcycles - Easy Rider (1969)

Two replicas of the motorbikes on display

While we're on the subject of iconic rides, the motorcycles from Easy Rider match The Italian Job's Minis when it comes to icon status.

Two copies of each bike were made for the filming of the counterculture classic, but three were stolen. Adding insult to injury is the fact that, due to the bikes being instantly recognisable, they were likely sold for parts.

However, Peter Fonda's Stars and Stripes bike survived the robbery, and is now on display at the National Motorcycle Museum in Anamosa, Iowa.

5. Bubo the Golden Owl - Clash of the Titans (1981)

Sadly rejected from the 2010 remake, Bubo the bleeping owl was a central part to 1981's Clash of the Titans movie, sent to aid Perseus in his quest to save Andromeda.

A beautifully made prop, we're very pleased to say that Bubo is still alive and well, and lives a peaceful life in a shared apartment with his owner. See the video for details (including a very special interview with Bubo).

4. Monolith - 2001: A Space Odyssey (1968)

A scale replica of the monolith standing at a fan convention

While choosing the imposing monolith featured in 2001: A Space Odyssey, Stanley Kubrick opted for a huge lump of black basalt rock imported from Scandinavia.  

Little is known of what became of the eerie rock, but we do know that Kurbrick originally commissioned Stanley Plastics to produce a transparent plastic monolith from Perspex for the movie - the largest single block of the plastic ever made.

This plastic block then spent years languishing at a film studio, before being repurposed as a crystal crown plaque created for Queen Elizabeth's Silver Jubilee in 1977. It now lies embedded in the wall of London's Thistle Hotel.

3. The One Ring - The Lord of the Rings (2001-2003)

Even the film's actors were fooled by the power of The One Ring

Contrary to its name, there are actually two original examples of The One Ring in existence. Made by New Zealand goldsmith Jens Hansen (who now produces a range of replicas), they were gifted to the central characters following filming.

Director Peter Jackson presented both Andy Serkis (Gollum) and Elijah Wood (Frodo Baggins) with the rings, with both under the impression that they were in possession of the sole original example.

2. Golden Gun - The Man with the Golden Gun (1974)

The golden gun was stolen in 2008 - it has yet to be found

Scaramanga (Christopher Lee) famously assembled his trademark golden gun from a cigarette case, a lighter and a pen in the 1974 James Bond classic.

Valued at £80,000 ($126,000), this gun was once stored at Elstree Studios, but was stolen in 2008. The thief later contacted a memorabilia dealer, who informed the police, but it has yet to be found.

When asked, Sir Roger Moore joked: "You'd better ask Christopher Lee about this. Search his house."

It is thought that the gun went missing when a crew member from the movie Kick-Ass was shown round the premises while filming was taking place.

1. Death Star - Star Wars Trilogy (1977-1983)