Playing games on the iBook is one of the nicest things. In 1999-2001, many Mac games for Mac OS9 came out and run well and smoothly on iBook. An example is the Tomb-Raider series, which can be had cheaply up to Tomb Raider I-IV and Tomb Raider-the chronicle used and mostly also start under OSX.
Strategy classics like Age of Empires 2 were also ported to the Mac and are still exciting to play today.