Evasi0n has made it possible for millions of iPhone 5 owners to jailbreak iOS 6 and use both the firmware and device to their fullest worth. Once you have installed the essential Cydia jailbreak apps (AppSync, SBSettings, iFile, Safari Download Manager, Folder Enhancer, WinterBoard, Activator), you are ready to start exploring the perks of a jailbroken iPhone 5.

biteSMS

biteSMS is an app that gives users frustrated with the standard SMS feature on iPhone 5 a chance to improve their experience. The app delivers a series of features to make text messaging on iPhone 5 better, such as scheduled messages and auto-forward, passcode lock, quick reply and compose, easy pick smileys, signatures and even templates. The app is free, but you can buy a full license and credits.
www.bitesms.com
http://cydia.saurik.com/package/bitesms

Zephyr

This is definitely one of the best 10 jailbreak apps for iPhone 5. Created by chpwn, this hack will improve and add multitasking gestures to your smartphone. Apple has increased the number of multitasking gestures for iPad, but not for iPhone and iPod Touch, leaving most iPhone 5 users stranded to just a couple of limited working gestures. Zephyr lets you swipe up to access the multitasking panel and left or right to switch between apps you are currently running, making double taping the home button a less common gesture. It costs $4.99 in the Cydia Store.
http://chpwn.com/cydia/zephyr.html

3G Unrestrictor

iPhone is used particularly for data, but Apple has integrated restrictions that don’t allow users to use 3G for certain activities, such as uploading Camera Roll photos to Photo Stream and in some cases FaceTime. 3G Unrestrictor is a jailbreak tweak that tricks the firmware into thinking apps are running on Wi-Fi, when they are actually using 3G speeds. The app needs a mobile internet plan to work.
http://cydia.saurik.com/package/com.crashx.unrestrictor3g
http://www.3gunrestrictor.com/