that is an easy one - assuming I could only have ONE animal - it would have to be DOGS.
I have had llamas, geese, Indian runner ducks, cats, and all have delightful, different personalities and I so enjoyed my time with all these animals however my dog once saved my life, and dogs are my constant 24/7 companions, so I would not hesitate in saying dogs.
The other animals, although I had strong bonds with the llamas, they were not with me 24/7 like my dogs are.
As cute as animals are I prefer to have not the responsibility of any animal. Have never been attached to the dogs or cats we have had over the years as I thought it was important that our children grew up with animals. However when they left home the dog & cat went with one of them.
It's not super imaginative, but I'd like a large dog, like an Irish wolfhound. Always wanted them, but they're too big for me (cost more to keep, wouldn't fit in the car etc. etc.). I'd also like a llama, an alpaca or a pet pig.