Scramby lets you change your voice free with its add on software.

Voice Changing Effects
According to Scramby,”Scramby is an add-on for Voice-over-IP (VoIP) telephones like Skype, Google Talk and Yahoo! Messenger that’s guaranteed to generate loads of devilish fun! It also adds new sizzle to online gaming. Scramby’s voice manipulation effects, joke voices and a huge supply of sound clips let you entertain your gaming partners with a new dimension of fun and variety in Online Virtual Worlds or while playing MMOG/MMORPG (Massive Multiplayer Online Role Playing Game) games.”

Where to get Scramby?
Get Scramby at this link.