It depends what your doing. Are you looking for a pet or live stock? I have a dog and fish (A betta and a 30 long- 30gal.=12x36x16) The tank is relaxing and I have a 'river fish' set-up with Danios, catfish, crayfish, and others. I like a dog as a pet because he's a good companion. I take him out with me a lot. Cats are good if you want to have a companion at home. Birds (especially Parrots) have a long life span and you should think long and hard before getting one. Same with Tortoises. You need to study diets ahead of time if you decide on an exotic. And make sure there's a vet in your area that can care for an exotic. Some will specialize on reptiles, others in birds, etc. Any pet can learn a trick (even fish!) But, if you have allergies or an abhorrence for high pitched noises, think again about fur and birds. Hope this helps...
Here's a sad note: People love parrots, but they do live long. One woman had a parrot who she loved and he loved her. She died. The parrot went to her kids, who didn't want him. They gave it to a friend, who couldn't care for him. Meanwhile, he was grieving. He started to lose his feathers. The friend passed him to someone else, who loved him, but wasn't able to keep him for long. He finally came to the pet store where someone else got him. She came back to the store a few months later to get another bird. Charlie (the Macaw) died. She didn't know why he wouldn't eat and didn't bother taking him to the vet. He was 32. He could have lived to 60 or even 75. Parrots are very smart and develop strong ties with their owners.
)