Redsn0w has been voted the most popular jailbreaking tool for many years, and for a very good reason. It is able to jailbreak ALL iOS versions, and Redsn0w 0.9.15b3 version can jailbreak the latest iOS version too.
Until this time, the latest iOS version is the 6.1.3 iOS, and it still gives issues to the jailbreaking community. When this version was released many people urged to update their iOS devices and they found out that neither they could downgrade to a previous jailbreakable iOS version nor jailbreak it. During this time two jailbreaking tools were available, the Evasi0n and the Redsn0w 6.1.3 jailbreaking tool.