I had written a “must have WordPress plugins” before but it got really old. Here is my 2013 list of must have WordPress plugins!
Akismet: protects your blog from spam
All In One SEO Pack: still needed, even though I don’t really use it to the fullest.
Better Delete Revision: you can limit the number of revisions saved in your DB in wp-config. I use this plugin to quickly remove the revisions from time to time.
EWWW Image Optimizer: I dropped smush-it because of the image size limitation (my photos are pretty big) and I now use EWWW, it also compress all the thumbnails.
Faster Image Insert: image insertion in WordPress has really improved and gives you a lot of new functions, but I still don’t like using it in a lightbox. Faster Image Insert adds an iframe under the editor, and you can directly access all your images from here.
FV Gravatar Cache: as its name says.
Jetpack: I don’t use all the sub-plugins provided by JetPack, but Photon is great. It hosts your images on WordPress.com CDN and saves your bandwidth. I hope improvements will be made to avoid broken images... I also use Stats, Shortlinks, Sharing, Contact Form
Google XML Sitemap: great plugin to manage your sitemap.
Search Regex: so far the best search and replace tool I’ve found.
Simple tags: for terms management on WordPress. The bulk editing of posts tags and categories is great.
TinyMCE Advanced: the WordPress default editor still needs improvements...