As a child I often mistook it for being my tonsils. What is the purpose for this little bit of glottal skin in the back of your throat?

Well, I know it's formed during embryonic develpment from the tongue pulling away from the lateral palatine processes, and the processes eventually fuse (grow together). If they fail to fuse, the child is born with a cleft palate. So, even tho the uvula is about as usefull as an appendix it's merely the by-product of a normal development.

Besides that, if we didn't have one how funny would cartoons be if they couldn't show the dangling appendage when someone was screaming?

It's used for making certain sounds in many different languages. Monolingual English-speakers probably don't need it though .
And it's used for snoring, but that's more of a disadvantage, at least for your partner .