One of our favorite, and probably most used, new jailbreak tweaks is named Zephyr by well-known developer chpwn. Zephyr has completely changed our experience with multitasking on the iPhone. Instead of double-tapping on the home button to bring up the multitasking switcher, Zephyr makes the whole experience much smoother by enabling single-finger swipe gestures.
The purpose is simple, but genius: swipe up from the buttom of the screen to bring up the multitasking app-switcher (instead of double-tapping the home button), and swipe left or right to flow back and forth between recently opened apps. You also have the option of disabling the tweak in certain apps where it might be a distraction (games, etc.).
Apple implemented similar gestures on the iPad but left iPhone and iPod Touch users in the dark. But, no need to fret. Zephyr does its job, and it does it damn well. In fact, we wouldn't be surprised to see the tweak implemented in iOS 6, as Apple has "borrowed" jailbreak tweaks and ideas in the past. Check out this video made by chpwn himself demonstrating the awesome tweak: