Okay, now that the DMG has dropped, and people can use its monster creation guidelines, let's have a challenge in seeing who can create the best version of a monster that a poster makes up (witha specific challenge rating and/or basic ability desriptions). I'll provide the fiesr challenge:
Abominable Dugong (CR5)
If you don't know what a dugong is, Google it (I hear there's a nifty song about them on YouTube). What makes it abominable? I'll let you guys get creative with that. 
Read that one flame-thread, then design a Tarrasque to make its OP happy. 
Not everyone has their DMG yet 