I just Googled 'the worlds biggest (human) penis' and it turns out to 13.5 inches.
I'm not bored or anything, just at work and it came up (ahem!) 
Important news
Strange I Googled the same thing and it came up with Ricky... better not erm Tony... no thats a can of worms er um... 13.5 inches aswell *phew!*
And the biggest twat?
Too easy.