I like ferrets, they're fun and can be litterbox trained. I had 2 growing up. Anna was good and used the litterbox and was a nice sweet ferret. Bailey was a brat, and she pooped on the floor. She was bad
but we were all so busy and no one took much time to train her. My dad eventually gave her to his friend who lived in the country and was single. He trained her to potty outside and scratch on the door to get in. He adored her, and he gave her a better home.
I really like rats, about the only downside is their lifespan (3 years tops). They can be litterbox trained (mine were cage trained, they'd go back to their cage to potty). They come when called, and can learn to do tricks. They don't chew cords like some small animals, they really don't chew much at all. They never bite either (unless abused).
Chinchillas can't really be let to run loose. They chew everything, and they poo everywhere (like someone else said, though, it's hard and dry and vacuums up). If you can get the room completely chin proofed then they are a ton of fun to have running around. They're good pets, I've had them for 9 years, the age of my oldest. They live anywhere from 10 - 20 years. They're not cuddly, but they are friendly. They'll come up to you and interact with you, but they really don't like being picked up and held. My 9 year old is the exception, you can hold him and pet him and carry him around the house all day and he's happy.
I don't think a dog is right for you, they really like having someone around alot. My vote if for a pair (trio?) of rats. Females are more cat-like, more independent and flighty, but still very sweet. Males are lap dogs, they just want to be held and cuddled and scratched under the chin. I miss my rats. I can't get more now because my dachshund would eat them.
Dawn