The Google system for comments. I wish it had more features. Like "Reply to this," less space in between comments and other things. I found this comment form that has all that! You don't need to have a Google account to upload your avatar or profile picture!
Disqus is a comment form embedded at the bottom of each post. One doesn't need to leave the page to write a comment anymore. Let me know what you thought of it, quicker comment form?