What is the best voice changer application?

I have a mac, and i saw something called JALLLER CHRONICLES on youtube. Heard of it? If so, yu know how funny his voice sounds??? He inspired me to make movies of the same kind, but my voice is not funny. I was wondering, what is the best voice changer application to use to record and change my voice? I've downloaded loads of things, but they all turned out as files. PLEASE ANSWER THIS QUESTION WITH CONFIDENCE, AND TRUTH. I NEED IT TO WORK!!!!!!!