I worked in a pet shop for many years and also kept a lot of pets myself.
I love the guinea pigs the best.. they are so cute and cuddly and really love to be handled and petted. But I am super allergic to them so can't have them as pets!!!
I did not like the rabbits. They looked so cute.. but they were really dirty and smelly.. the males sprayed urine over everything, even people.. the females would bite and fight and be grumpy. They don't like being picked up or cuddled and will kick and scratch when they want to get down.. resulting in my covered in lots of huge scratches!
The chinchillas were really cute.. but they don't like being held or petted. More a pet to look at.
Same with the chipmunks.. plus they STANK!
The reptiles were interesting.. but boring after a while as they don't get attached to you as their owner.. and buying live insects and dusting them with vitamins all the time is annoying.
Hamsters were OK.. but if they bite it really hurts the most!
Rats were the BEST.. So intelligent and would follow me around the house and love to climb up my leg and sit on my shoulder. They liked handling and were very social and got attached to their owner. But I found lots of other people did not like them just because they had a tail.
Mice.. lovely and cute... but really really really stink!!!!!!!!! Clean them out.. after one hours they smell again.
Fish.. nice... relaxing... but I consider them more decoration than a real 'pet'. Its also a pain if something goes wrong with the filter or heater etc or they get a disease.. they seem to always get a disease whenever you add any more fish.
Gerbils.. nice.. no smell, active and fun to watch. OK to handle. but they are not very intelligent or affectionate... but come in nice range of colours and super easy to care for.
Small birds are nice.. interesting, beautiful and easy to care for.. but not really a hands on pet and can be noisy and get seeds everywhere.
Other animals like hermit crabs, stick insects, snails... DON'T BOTHER.. they are not pets.. they look interesting but they do nothing and you will soon get bored with them.
Things not to get EVER.. TURTLES.. really dirty and need so much care.. and get sick easily if you laps in any aspect of their care.
PARROTS.. they are too noisy and if you can't be with them 24 / 7 all their life they get psychological problems and pull out their feathers.
Hope that helps!