Here at Paul Fraser Collectibles we concentrate on the most interesting and valuable items from their field of collectibles, and tend not to spend too long considering the more random items that people hoard - after all, some people's collecting tastes can be extremely peculiar, and it's rude to stare.

Nevertheless, even amongst those items which are historically significant, ingenious or exquisite, there are those which are also just a bit ...strange. Here we've picked five of our favourites:

A head on which to rest your head

The Asmat tribe of Indonesia, like most of the peoples of the world, felt that honouring and respecting their dead was terribly important. In their case this involved 'ndambirkus' - ancestor skulls.

The tribe would carry the skulls to pay tribute to them. Perhaps more surprising is that they were used for apparently quite mundane, practical purposes, notably as pillows.

In November last year, one such carefully preserved skull went under the hammer valued at £10,000.

Is it a car...? Is it a plane...?

In the 1930s, flying was still magical and the jumbo jet was a long way off. The idea of flying cars had worked its way into some science fiction stories.

In Frank Skroback's case however, it had worked its way into his garage.

Frank Skroback's flying car

Skroback got the idea from studying the concepts of former furniture maker-turned-aircraft designer, Henri Mignet. Mignet had invented the tandem wing monoplane.

Skroback's idea was to modify Mignet's design with a multi-purposed vehicle: a car useable on both the ground and air, using the roads as runways.

Ingenious, if not exactly elegant, Skroback's creation sold at Red Baron's in March 2010 for over $65,000.

I see what you're thinking

Collecting memorabilia associated with genius Albert Einstein cannot be considered eccentric, indeed anyone owning a letter by the man who discovered general relativity would probably consider it one of their prized possessions.

Some examples are stranger than others though. On December 3, 2010, two X-rays showing both a frontal and profile view of Einstein's skull went under the hammer Julien's Auctions. They had been listed at just a few thousand dollars, but bidders ignored that and pressed the images all the way up to $38,000.

We went for the more tasteful example here - X-rays of Marilyn Monroe's chest and President John F Kennedy's pelvis have also drawn great interest at auction (separate images, not the two of them together).

The $53,000 tin can

"Shoot him... He roars, flashes, and goes away... Soon comes back to you!"

This description is not of an irrepressible dinner guest, but rather is taken from the box of a mint condition Gang of 4 Target Robot toy from Japan.

Certain Japanese toys, for example those of the inventive but relatively short-lived company Popy, can be extremely valuable, as we noted when covering the collection of Mark Solondz. If properly looked after they could make an excellent investment.

Japanese Target Robot

The boxed example proved to be the star of Dan Morphy's February 2010 auction, bringing $52,900

Feed it with gold leaf?

Sotheby's autumn sale of Important Watches in Geneva in November 2010 offered a wide range of extraordinary timepieces, with Patek Philippe particularly well represented.

However, the most eye-catching piece on offer wasn't a watch at all, but appeared to have crawled in from another auction altogether, though it is a piece of jewellery which required great engineering skill.

Jewelled Ethiopean caterpillar

The 'Ethiopian Caterpillar' is a rare gold, enamel, diamond-, pearl-, ruby-, emerald- and turquoise-set automaton, thought to have been created at some time around 1820.

It went under the hammer valued at the equivalent of $467,000.