Revoice Pro - Revoice Pro is an audio plugin used for vocal tuning, time correction and ADR.
Voicemod - What are the voice changers? How do these work? Are these illegal? What is a soundboard? Find all the answers here. Voicemod - The Best FREE Voice Changer
Kontakt - With KONTAKT 6, you can sound like a snare drum, a symphony orchestra, or anything in between, from a universe of sampled instruments.
Clownfish Voice Changer - Clownfish Voice Changer is multiple voice changing software for various chatting and gaming platforms.
GSnap - With GSnap you can get an auto-tune effect.
LinuxSampler - LinuxSampler - free, open source pure software audio sampler with professional grade features.