Where are your events coming from?

I’m curious to hear, besides your core product, which data integrations have you made with Amplitude i.e. what is the source of your events? My list is below (% of my clients doing each in brackets)

1. Core Product: Front-end (100%)
2. Core Product: Back-end (36%)
3. Push Notifications Tool (29%)
4. Mobile Marketing Platform (21%)
5. Email Tool (14%)

FYI - my clients are typically seed/series-A stage, so often have integrations planned but not yet done!