I had a pet rat, and well as 2 rabbits over the course of my childhood... Can say that the rat was great; easy to litter train, train to do tricks... He was friendly and eager to please, and slept in a hammock made out of a handkerchief in his cage. Cons: they can be stinky, and - sorry - the male ones have pendulous tackle *ahem* that makes them a bit less 'cute' when they reach maturity. Rabbits: it's difficult, because it's quite personality-dependent. We had an amazing large rabbit (maybe a Chinchilla/Rex?), a mature male we adopted, and he was friendly, easy to train and loved snoozing with you and being held. Only con was that he engaged in the occasional arm/cushion hump. We had another, but a dwarf bunny, that my sister picked because she was 'sassy', and she was a biting, running-away, wire-chomping, litter-kicking nightmare. From my experience (and this is still pretty limited), males can be less aggressive, and the big ones can be calmer and quieter than the little ones, a bit like some dogs! I'd go for a rat to start out, perhaps! Good luck!