npm ERR! Invalid name: "@angular/core" when following the Angular 2 Quick Start
Since my comment answered this question I will provide it in the form of an answer for the future people visiting this page.
After a little Googling I found two pages having the same problem; page 1 and page 2. It seems there's a bug in some versions of NPM so simply upgrading to a newer version should fix the problem:
sudo npm install -g npm
Downgrading could also fix the problem:
sudo npm install -g npm@<version here>
Hope this helps