Hi from the other thread!
My EC's were mostly long-term volunteer positions on my campus. I do media work so most of it involved photography/videography and marketing stuff for clubs and charities. I have also worked part time in customer service for 6 years. I had no research experience.
Obviously everyone has a different experience but I don't think there are specific EC's that help more than others. As long as you can talk about it and they can tell you're genuinely passionate about what you've been doing, its fair game imo.