Wiinote lets you control Keynote (and now other applications) with your Wii Remote. Wiinote sports a simple, uncluttered interface which makes configuring and using Wiinote as simple as possible. Wiinote lets you customise which Wii Remote button triggers which Wiinote action; you can assign any action to any button.
Version 0.4.0 adds a number of new features, including support for Mac OS X Mountain Lion and Microsoft PowerPoint.
Mac OS X 10.4/10.5/10.6/10.7/10.8
Free to try