Loging in with JUST Facebook

Is there any Plugin that allows my users to login JUST using facebook? Like, without registering. When they click the Login button, I want them to see only LOGIN WITH FACEBOOK . Much like here : https://9gag.com/signup

What I have at the moment is this : http://gyazo.com/36f7858f1bb89ee5fd0c764f6293b5dc The Facebook button is too small tho, I want it to be bigger and sort of IN YOUR FACE -ish. I completely disabled user registration anyway with Wordpress, I just allow them to use my site with Facebook logins.

By just clicking Sign Up With Facebook and Allowing the App to access their account, users would be able to post on my Wordpress.

So the Million Dollar question is: How do I make my Facebook Login button bigger OR remove the wordpress login and just leave LOGIN WITH FACEBOOK . I am looking for this plugin, I want to buy it if it exists on Code Canyon.

~Regards, Smexy

bump