I have built couple of extensions that I sell and support:
Highly customized ecommerce project developed using Magento 1.9.3 for fontvellaencasa.es. Theme design provided by another agency.
Some of the tasks involved:
Online store with custom graphic design and complex Magento configurations. Magento Multi-Store Installation with 3 different stores, themes and extensions.
Custom online service to probate a will online. The project uses Magento 1.9 as the backend. Most of the customizations were made through a custom extension developed for the project purposes.
Custom Extension development for Hivewyre.com. The Extension was developed for Magento 1 and Magento 2.
Extension that installs Facebook Pixel on Magento Stores. The extension uses Magento observers to track the events accurately.