A recent tweet that I found funny - "Every time a conf organizer accepts a talk about #IoT using JavaScript ... somewhere in the world an IoT/embedded developer ... dies !"[1].

On a serious note though - Does anyone know a mass manufactured product (based on a uController) that actually uses anything other than C/C++?

Rust is a strong contender too, surprised to not see it mentioned here. See an older discussion about Rust on ARM Cortex M[2]

1. https://twitter.com/ppatierno/status/894575063562936321 2. https://news.ycombinator.com/item?id=14071282