One of the most important things when you start a company is to be able to communicate with your customers and get feedback on your product. That's why the first thing I would use is https://crisp.chat/ on my landing page
Also, I now wake up to a lot less people telling me to "fuck off." :)
I sometimes see websites try them but I cannot remember a single site that kept it going.
I could maybe see using one on a pricing page or something like that, if I couldn't figure out which plan was what I needed.