Star Wars Episode 3: Revenge Of The Sith Easter Egg - That Lightsaber's a Bit Familiar...

At the beginning, when Obi-Wan and Anakin are captured by Grievous aboard the Separatist cruiser, and Grievous takes their lightsabers and says "Your lightsabers will make a fine addition to my collection," look closely at the lightsaber handles. One is Anakin's, but the other is the distinctive lightsaber hilt belonging to none other than Luke Skywalker. Obi-wan fights on board the cruiser with this lightsaber, but unlike Luke's it is blue. However, the handle is definitely different than Obi-wan's standard saber.