Most of us have probably worked in a customer service role at some point in time. Discounts all depend on the type of place you're working at, but generally there's at least some room for discounts.
Me? When I worked at Starbucks and a friendly regular customer wanted a basic cup of coffee, I'd just give it to them for free, because I appreciated them not asking me to make them something complicated.
A recent Twitter thread discussed the wide world of customer service discounts.