When I graduate I will get a small animal as a reward, but I can't decide which on. I'd like to have rabbits because are very very cute, able to be litter trained, and can be trained in other ways as well, but they prefer to be free roam (especially if they are large like the flemish giant I want), meaning that I have to rabbit proof my whole apartment. I'd like to have guinea pigs because they are adorable and are comfy in a (albeit quite large) cage, but they can't be litter trained. I'd like to have ferrets because they are little cat snakes and aren't as skittish as other animals and can hold their own, but they are very hyper. Help, I can't choose.

I know you don't like mice/rats so I won't suggest that, although I did adore my own mice when I had them. There's something kind of magical about letting them walk around on you and sniff you. Maybe a hamster, guinea pig, or ferret. Rabbits are good and cute but I hear they make lots of poopies and I personally wouldn't want to clean that up. Basically any rodents (or animals that are like rodents) will be smelly and messy. The good thing about the smaller ones is that they're confined to a cage so you can somewhat contain the smell, but I can't guarantee it. Another thing to consider if you're going with small rodents is the hamster wheel. It's necessary, but you want it to be big enough that it doesn't make them arch their back downward when they run on it and you don't want it to hurt their little feets. Of course there's the matter of having a large enough space for them to be comfortable and if they're biting the cage bars or climbing the top of the cage then it's probably too small. There's also the cost of buying/replacing the bedding material in the cage. Also apparently hamster balls aren't the greatest and I definitely wouldn't recommend using one since you have a dog.
Anyway, sorry for rambling, I'm no expert or anything but I hope this helps. If you get a rabbit then I imagine you won't need most of this anyway.