Well the funny thing with Quark is, that watching the show as a child I really really hated him. I thought he was just annoying, with everything about him being about making money, mistreating women and so on. It's only when I got older that I realized what a brilliant character Quark actually is, and that his relationship with Odo really is one of my favorite things about the show.
When I rewatched it some years ago, I was surprised to see so many great Odo/Quark moments even in the first season. This show was blessed with brilliant writing and equally brilliant actors. Auberjonois and Shimerman were such an integral part of the show.
My favortie Quark episodes would have to be "Rules of Acquisition", where we got a first hint that Quark was more than just your typical Ferengi, "Business as Usual", which once and for all established that he had a conscience, and "Profit and Loss", in which he got a nice romantic backstory that really allowed Shimerman to shine.