Game Overlay
Game Overlay helps get back some of the multi-tasking functionality lost when playing full-screen games. It allows you view and interact with windows outside the game, but without "Alt-Tabbing" and requiring the game to reinitialize its graphics. It does this by actually rendering the window... Overlay the GUI for external voice applications such as TeamSpeak or Ventrilo. ... Forget about writing down or printing cheat codes... ... Overlay a semi-transparent e-mail client over the game! ... Simply copy and paste them into Notepad, then overlay it!
http://www.gameoverlay.com/files/GameOverlaySetup.exe - 2Mb - Download - Screenshot

MorphVOX Junior
Pure Voice Changing Fun! MorphVOX Junior is a free voice changing tool that will change the way you play games or chat online. Change your voice to sound like man, woman, or tiny folk. Make your friends laugh with the number of sound effects that you can broadcast online. ... This voice changer works with all the popular game and online chat programs including Skype, AIM, Yahoo, MSN, GoogleTalk, TeamSpeak, and Valve games. ... You can even send out screeches and drum rolls with a push of a key, mouse or joystick button.
http://www.screamingbee.com/FreeDownload.aspx?i=4865 - 2Mb - Download - Screenshot

AV VoizGame
AV VoizeGame is an innovative voice chat tool which changes your real voice to disguise your real identity and play in different characters of Online Role Playing Games. You can freely use the fabulous library of nickvoices including 5 for male input voice (Pleasant Girl, Prudent Girl, Balanced... This game chat weapon is compatible with most chat application such as Ventrilo, Teamspeak, Roger Wilco, Yahoo Messenger, MSN, AOL Instant Messenger, Skype, etc. ... and famous online games from World of Warcraft, MU to Counter Strike and EVE.
http://www.audio4fun.com/download/voizgame-aff.exe - 2Mb - Download - Screenshot