My favourite Hidden Gem is... my bank! I recently discovered that ASB - and probably other banks too - have coffee machines onsite, free for the use of customers. The machine makes pretty good, it even seems to use beans rather than instant mixes. So if I happen to be at a mall (rare as that is) and fancy a coffee, I head to the bank! While I'm there I can also check on my bank balance to remind myself of the day's budget and state of the savings, while waiting for my lovely free mochaccino to bubble into a takeaway cup!
All I have to do is walk in! I usually try to demonstrate that I am an actual customer though, rather than waltzing straight to the coffee machine!