Libyan forces allied with the U.N.-backed government fire weapons during a battle with IS fighters in Sirte, Libya, July 21, 2016. (Photo by Goran Tomasevic/Reuters)

Mosha, the elephant that was injured by a landmine, has her prosthetic leg attached at the Friends of the Asian Elephant Foundation in Lampang, Thailand, June 29, 2016. Mosha was 7 months old when she stepped on a land mine near Thailand’s border with Myanmar and lost a front leg. That was a decade ago... (Photo by Athit Perawongmetha/Reuters)

A chimpanzee relaxes in the shade at the Safari Park as the popular attraction prepares for the upcoming Jewish festival of Pesach (Passover) on April 14, 2008 in Ramat Gan near Tel Aviv, Israel. (Photo by David Silverman/Getty Images)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

U.S. Air Force pilots with the Thunderbirds perform the calypso pass maneuver in F-16 Fighting Falcon aircraft during a practice session prior to the Gunfighter Skies air show at Mountain Home Air Force Base, Idaho, September 19 and released September 24, 2014. (Photo by Tech. Sgt. Manuel J. Martinez/Reuters/US Air Force)

The eighth annual Nipponbashi Street Festa stamped Osaka March 20, 2012 (Nipponbashi is Osaka’s geek district – much like Akihabara is for Tokyo). Cosplayers turned up in colourful outfits, dressing as characters from their favourite manga, anime, and video games. The street was closed to cars, and otaku flooded the streets, snapping pics, cosplaying, and hanging out.

Spanish bullfighter Manuel Jesus “El Cid” is seen through a small window of a door as he performs a pass to a heifer during a “tentadero” (a small bullfight to check the bravery of calves and heifers which are not killed) during the first International Biennial of bullfighting at Reservatauro Ronda cattle ranch in Ronda, near Malaga February 17, 2013. Spain's parliament voted last Tuesday to consider protecting bullfighting as a national pastime, angering animal rights campaigners and politicians in two regions where the sport is banned. (Photo by Jon Nazca/Reuters)

A People's Liberation Army (PLA) commando jumps through a fire hoop part of an exercise during an open day event at the Ngong Shuen Chau Barracks, the PLA navy base in the territory, in Hong Kong, China, 01 July 2015. Thousands of visitors attended the PLA open day yesterday and today to mark the 16th anniversary of the handover from British rule. (Photo by Jerome Favre/EPA)