I'll bite.
Like you, I was working on a lot of Wordpress and ModX sites, along with some straight PHP. I've always enjoyed the creation process, not just using someone else's creation, though, so I started working on bigger sites as I got the chance. I got into CI around 2006, IIRC and have loved it ever since. I've used Slim and Laravel, looked at things like Yii and Symfony, but always come back to CodeIgniter. It's light-weight, declarative (less magic) and better performing than most of the others, while still providing all of the tools I need on a daily basis.
With it I've created several fairly large sites, many of which, unfortunately, faded away as their owners weren't able to make them successful for one reason or another but they include sites like:
1) A portal for bass fishermen, with forums, profiles, classified ads, daily updates of lake information, etc.
2) A regional sales site for autos from many dealers. Admin area, dealer area and public area. Pulled in feeds from 40+ dealers, standardized the autos in the database, provided a way for customers to interact with dealers through "anonymized" email, calced the search results from a proprietary formula based on dealer usage of the system, in part, allowed search to factor in customer's down payment, credit rating, etc as they searched for autos by payment, though they could filter the search. Used both MySQL and MongoDB.
3) A loan-related database for someone who bought and sold people's information that, at last count had 20 million emails in the TPS (don't call) database and around 2 million people in the database. Input and export CSV files. Normalizes all data on the way in. Very customizable query system to allow owners to filter the data almost any way possible, including not re-selling data to the same person if they already bought that information 'x' days/weeks/months ago.
