I guess I would say small birds. I know a lot of people like fish but they are messy and their tanks tend to smell bad. At least with small birds, it is fairly easy to clean out their cages.
Insects are probably the easiest. Things like hissing cockroaches and spiders. I know that is not for everyone though so keeping a smaller fish tank that is balanced (to be self-cleaning) is probably ideal.
I had one growing up and loved him. I named him Nibbler. He lived to be about 6 years old which is considered long for a small rodent. I have since wanted another one but never actually got one.
I mean to me, the best pet has to be one you can interact with and since cats and dogs are off the table, I would say the next best option is bunnies! They are technically "caged" though some people do train them to be free-roamers inside their homes. It just takes work but they still need to be crated at night.
@thirdstrikeiii I still think insects are easier but I know not a lot of people like to keep those as pets. I grew up with a brother who had a collection so I never viewed it as strange.
