This is a fun question this month. Speaking as someone with "caviar dreams and a cheeze-whiz budget", I've always wanted a koi pond. And the funds to hire someone to take care of it.
What would you do in your garden with unlimited funds?
Oh, to have a nice garden railway, with a live steam train going around mountains (mounds) with California native plants everywhere!
(Photo: Calochortus argillosus)