What rodents make the best pets?

I'm researching different small pets because I live in an apartment and I wanted some thoughts on which rodents make the best pets. I'm considering rabbits, guinea pigs, rats, and perhaps ferrets although the legality is just a bit questionable at this point. I'd prefer a pet that can be affectionate in some way, if that helps. What are the pros and cons of these different pets? Any thoughts/opinions/comments would be appreciated.