Strange and exotic weapons are a recurring theme in science fiction. In some cases, weapons first introduced in science fiction have now been made a reality. Other science fiction weapons remain purely fictional, and are often beyond the realms of physical possibility. At its most prosaic, science fiction features an endless variety of sidearms, mostly variations on real weapons such as guns and swords. Among the best-known of these are the phaser used in the Star Trek television series, films and novels and the lightsaber featured in the Star Wars fictional universe.