Sounds and Editors

I need to find a program that can edit sound effects (something that can increase/decrease pitch), is there any free software that can do this? also, i am in need of sound effects for my gun mod, particularly for some sort of plasma cannon burst.

Try GOLDWAVE, it's not free (US$45.00), but they offer a trial version

http://www.goldwave.com/

Audacity is for free