Scimitars are weak, but fast, slashing weapons. They are identical in damage and attack speed to daggers and maces. Scimitars are generally the most expensive of the three 'fastest' weapon types, and they lack the prayer bonus offered by maces. Nevertheless, they remain popular due to the reputation they have gained over the years as being the ideal training weapon.
Scimitars are made with the Smithing skill, purchased at a scimitar shop identified with the scimitar icon on the map, or bought from another player. One scimitar shop is Zeke's Superior Scimitars, located in Al Kharid. Unfortunately, it only sells bronze, iron, steel, and mithril scimitars. There is also a members-only scimitar shop located in the Ape Atoll that is only available after completing the Monkey Madness quest. This shop sells Dragon scimitars.
It should be noted that, as with most off-hand melee weapons, off-hand scimitars do only half the damage as their main-hand counterpart, as well as being equipped in the shield slot.
While Scimitars offer higher attack speed, they are slightly weaker than longswords. There is a 3 second delay between blows with a longsword, whereas with a Scimitar, the delay is only 2.4 seconds. This equates to 20 attacks per minute with a Longsword as compared to 25 attacks per minute with a Scimitar. The extra 5 blows per minute usually outweigh any damage boost a longsword will give. However, the extra five hits, due to the lower damage bonus of a scimitar, may be 0s or low hits, as opposed to stronger hits with a longsword. Conducting accurate tests to compare the two weapon types, although attempted, have never brought about conclusive evidence of superiority due to the many factors that must be accounted for, such as enemy defense and Attack level, along with weaknesses to certain attack types. For the most part, it's merely personal preference as to which is a better weapon. However, there are factors to consider in choosing which weapon to use: those who want attack speed over power should choose a scimitar; those who want power over speed should choose a longsword. Due to changes brought about during the Evolution of Combat, however, most (if not all) weapons have been balanced to have an equal damage per second, making attack style one of the only things to consider when choosing a weapon.
Prior to 12 April 2011, the dragon scimitar was the only scimitar to have had an animation update that distinguished it from all other scimitars. This has been updated, so that all scimitars share the updated animation.
When you ask Zeke in Al-Kharid if you can buy a dragon scimitar, he tells you "Only the banana brained nit-wits who make them" This is a reference to the monkeys from Ape Atoll who create them.