A chihuahua sounds like a lovely pet! Despite having two small dogs of my own, I cannot stand how yappy tiny dogs are! Rabbits also make amazing pets though. A rabnit would be really fun, and you could get a single one if you could perhaps find one who doesn't quite like other rabbits and thus can be housed alone with extra TLC. I have one rabbit who is super aggressive towards other rabbits, but the sweetest little girl towards me
She was tried several times to be paired up by the rescue group she was with, but ended up nearly killing the other bun every time she saw him
you could end up using a C and C grid cage for some other critter and have a free roaming rabbit! My bun free ranges in my house and she never causes any trouble, in fact my dogs are more destructive than she is!