My coworker has been getting on my nerves so I'm going to call him a rat-faced goblin.
Are you sure you want to do that? What do you hope to accomplish by insulting him?
I want him to know how I feel. I don't really like him and I think this is an appropriate name.
It is very rude to call a colleague names, and it's highly inappropriate for the workplace. If other people find out that you're saying this kind of stuff you could be fired, so it's not worth it.
He's an asshole and deserves it.
If you don't like this guy then you should just try to limit your interactions with him. Insulting him isn't going to make the situation any better.