The one thing that sets MacBooks clearly apart from most other laptops that I've used over the years is an expertly designed trackpad. While there could still be some improvements, it's definitely better to use than trackpads on other laptops. Since Apple released the Trackpad and Magic Mouse, the MacBook trackpad experience can now be ported to iMacs and Mac Pros.
1. Better Touch Tool
Andreas Hegenberg created the Better Touch Tool and it's one of the most comprehensive apps to customize your trackpad and Magic Mouse. From three finger taps to tip taps, there is a lot that you can make your iOS pointing device do. At the beginning, using this tool can get somewhat overwhelming, but once you get used to it, there are a wealth of possibilities. You can even program your own custom gestures, which I really liked. This is due to the fact that the trackpad recognizes multi-touches.
MagicPrefs was designed to improve the overall functionality of the Magic Mouse. While many people have eschewed the Magic Mouse for the Apple Trackpad, there are users who still prefer having a mouse around. Using the gestures comes with a learning curve, but once you know them, they become somewhat intuitive. Tracking speed can be augmented by up to 200%. The overall touch surface of the Magic Mouse is quite smaller than the Apple Trackpad, and in my opinion, the Trackpad is the better buy, especially when combined with something like Better Touch Tool.
JiTouch was improved by adding more support for the Magic Mouse. In the latest version, you can access fully customizable actions, gestures, flicking quickly between Spaces in OS X, and tab switching. Unlike BTT and MagicPrefs, JiTouch isn't free but costs $5.99.
MouseWizard allows you to give your MagicMouse up to six extra buttons. It also supports 'pinch', 'bloat', and 'tap to click' trackpad gestures, as well as some special gestures like 'coverup', which will make your Mac go to sleep. This is simple app to setup and allows users to access good features without having to bother with advanced features. It costs $5.