I've had all kinds of fish tanks, freshwater tropical, saltwater, liverock. But my favorite was when I collected the fish myself from local lakes.
I've had two different native tanks. The first had two bluegill, two crappie, and a largemouth bass. I put a dozen minnows in the tank that I bought from a local bait store, boy what a feeding frenzy that was! The second contained six pumpkinseeds (a very colorful type of sunfish). I had a sand substrate and live plants I grew from bulbs. Was a very pretty tank. However, once the pumpkinseeds started trying to breed, they got too aggressive, so I released back where I caught them.