I am a fan of Reddit, but I am overwhelmed by it's horrible web interface. My idea: organize it in an interface similar to Windows File Explorer. Reddit is the root, each sub-reddit is a folder in the tree, a directory, each post a file.
The program (reader) could have a preview pane, like Explorer, for media such as photos and videos. It would also have a "Favorites" or "Shortcuts" section for subscribed Reddits. Possibly even a download function, although that may be questionable.
Simple, clean, easy to navigate, with a nighttime theme of light text on a dark background, or just follow Windows.
I would sacrifice a beer to Dionysus for this.