Strewth

I think, as with nearly all things Tool, his significance is likely highly subjective. However, it's reasonable to keep in mind that (and this is just based on what I remember of this little bugger) he seems like all he exists to do is to bite and consume. Things with just teeth and no eyes tend to have that quality. (Like the Corinthian from Neil Gaiman's Sandman, a man with teeth for eyes. His whole existence was based on engendering fear. Dream created him as the perfect nightmare; when he escaped into the waking world, he was a murderer who ate the eyes of his victims and basically launched the age of serial murder in the United States. He contributed nothing but pain for all his consumption.)

Looking at it from a toolish perspective, the little slimy toothy bugger probably would represent the destructive, selfish, and vampire-like elements of our personalities that hold us back, that keep us on the base food-sex-sleep level of the hierarchy of needs, preventing us from attaining higher levels and evolving as beings, connecting with others, self actualisation, etc. At least, that's what I got out of Schism. I'm interpreting from Schism, since it's the one I remember best, and I don't click youtube links. Ever.

But, basically, I think it's more what his significance is to you than anything.