We're going out for drinks and I'm thinking of not including one of my coworkers.
Did they do something that makes you want to exclude them?
Yes, they are a nuisance. They're totally incompetent and I'd rather not be around them.
Not wanting to include your coworker is fine since you don't seem to like them. It's normal to not invite someone you don't like to an outing.
I just cant stand their nagging.
It's certainly an annoying thing to deal with. You should focus more on the friends you will spend time with.