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!