SO many options! I generally prefer a lot of smaller fish as I enjoy the interaction of the fish with eachother. You mentioned oscar, so I assume you want to go bigger. My problem with that is you are limited to only one or a few fish. Not that it's always a problem, I just find watching 1 fish boring. Furthermore, I don't feel it's a good idea to get a bunch of fish when they are small, knowing you will intend to eventually rehome all but 1 or 2. SO you are stuck with watching them slowly grow into the tank, or buy find someone with the right, already mature fish. Now that's all just my opinion.
What are your thoughts or ideas? Anything you want to have? Anything you don't?