In Return of the Jedi Luke Skywalker used a secret compartment in R2-D2's dome to hide his lightsaber from the vile dezinens of Jabba the Hutt's Palace. As we all know R2 eventually launched the saber during the Battle at the Great Carkoon on Tatooine, surprising Jabba's henchmen and helping Luke save the day.
To make this figure, I simply took a POTF2 R2-D2 and drilled a small hole in the top of the dome in a near accurate spot as in ROTJ. I then took a Luke blue lightsaber and cut off the translucent blade and sanded down the hilt. Sticking the hilt into the hole, the hilt stands balanced on the third leg of the figure. To launch the saber, I simply pull down the leg, then thrust it back in pretty fast, it 90% of the time launches the saber straight outta the hole. Not the most technically apt custom of this version, I have seen more complex, but this works for me.