Easify Custom Product Options

This app replaced about a half dozen others for me. I have products which are highly customizable, as well as the need for making kits from individual SKUs. This app handles both just fine. I was able to get it integrated into the look and feel of my site pretty quickly.

The conditional rules are the best feature, allowing you to exclude certain combinations or show and hide stuff depending on earlier selections.

Their support has been responsive thus far.
You can use the custom HTML option to add iFrame videos.

My only issue is that the image insertion method requires uploading a new file every time, instead of allowing images that are already in my media library via URL.