To have a happy and successful relationship with your small animal it is very important that you make sure you choose a good fit. This starts with the species of the animal. While there are exceptions to every rule within reason, housing requirements and certain natural behaviors come with every species and should be taken into consideration before making an addition to your family. While you may find a dwarf hamster that would be great with small children, or a guinea pig that needs a special touch, there are universal elements that don't change involved in keeping different species of small animals.

Pros: Bunnies are a longer lived small companion, and average around 8-10 years. They can be litter box trained, and learn to do a variety of tricks. Bunnies have a big personality, and enjoy being part of the family (similar to a family cat or dog) more then many small companion animals.

Cons: Bunnies need a very large environment, as well as out of the cage time for exercise. Your bunny will need their cage and litterbox cleaned every other day, and they are the highest maintenance small pet. Many bunnies do not appreciate being carried around, and prefer to interact with their pets on the floor. A bunny is no more a child's pet then a dog or a cat is, they need to be part of the whole family. Bunny Proofing is important, as many bunnies will chew on wooden furniture, carpets, or cords if not properly 'house trained'.

Chinchillas
Pros: Chinchillas live for a long time, typically about fifteen years, which is great if you want a very long time companion. They can be kept alone and also do well in same sex pairs. They make very interesting pets, and a properly chinchilla proofed room provides a great playground. Chinchillas are odorless pets.

Cons: Chinchillas are very quick and require a gentle touch and generally like to be on the move rather then being held. They require large living spaces and cooler temperatures...below 82 degrees or they risk very dangerous heat stroke. Because they don't appreciate being held tightly or for too long, many chinchillas will not make a good pet for children. Despite being odorless pets, chinchillas can make a mess with their hay and dust bath.

Guinea Pigs
Pros: Guinea pigs have a very gentle disposition and will rarely bite, even under stress. Guinea Pigs are active all day, sleeping off and on, so are more likely to be awake when their humans are. They have more substance to them, making them easier to handle then many small animals like hamsters and mice. A guinea pig can make a good pet for a young child, as long as the child handles them in a guinea pig proofed area while sitting on the floor. Cages for Guinea Pigs can be made very easily and cheaply.

Cons: Guinea pigs can be easily injured by short falls and care must be taken when handling them not to drop them. They have very large housing requirements, and while these can be made very inexpensively, a pair of pigs needs at least 7.5 square feet of space. Care must be taken to make sure they get enough vitamin C in their diet or they can get scurvy. Store bought cages are generally not sufficient space for a guinea pig.

Rats
Pros: Rats are awesome small pets that are the most social with humans. While many small pets do more to tolerate your presence, rats have a great desire to be with their human companions. A full grown rat is big enough to be easy to handle, but small enough for almost any living situation. Rats can be free ranged in the house so long as everything is adequately 'rat proofed', they can be litter trained and can learn tricks. A well trained rat can ride on your shoulder. While rats are social animals, it is not entirely uncommon to find one that doesn't appreciate cage-mates that would be suitable for a solitary living situation. Rats can make very good pets for families as they are very disinclined to bite.

Cons: Children need to be observed with rats to make sure they do not pick up or restrain a rat by it's tail as it can very easily become injured. Some rats will scent mark by leaving a drop of urine as they walk, although this depends on the rat. They need plenty of toys and human interaction or they can become bored and depressed. Many rats will develop respiratory problems, and tumors are not uncommon.

Syrian Hamsters
Pros: The larger size of the Syrian Hamster makes them an easier pet for a child to handle, they tend to be more friendly and easy going then dwarf hamsters and mice. They can be taught simple tricks and are very clean animals. The variety of cages for hamsters makes for a very interesting environment to watch them in. Hamsters are solitary creatures and do best kept separately from other hamsters, making it easier for someone who only wants one small animal.

Cons: Hamsters are nocturnal and do not adapt to the schedule of their humans as well as rats or gerbils. A grouchy hamster is more likely to bite when disturbed then a happy hamster that got it's beauty sleep.

Dwarf Hamsters (Campbells)
Pros: Campbells Dwarf Hamsters can be kept singularly or in small groups, depending on the personality of the hamster. There are plenty of campbells dwarf hamsters that do not appreciate cage mates, and so if you are only wanting one animal they may be a good choice. When handled from a young age, Dwarf hamsters can be quite friendly. They are relatively low maintenance and very clean. Exercise is easy to provide with a safe running wheel.

Cons: Dwarf hamsters are quick and not well suited to small children who may lose hold of them. If they are not tamed from a young age they are much more likely to bite then many small pets. They require consistent handling to keep them tame or you will end up with a hamster that behaves more like it's wild relatives. Campbells dwarf hamsters are prone to diabetes and should be kept on a sugar free diet.

Dwarf Hamsters (Roborovski)
Pros: Robovski Dwarf Hamsters can be kept singularly or in small groups, depending on the personality of the hamster. Robovski hamsters get along well when raised together. Robovski hamsters are much less likely to nip then a Campbells Dwarf Hamster. They are easy to keep pets, as they are very low maintenance and take less cleaning when kept in a large environment. Exercise is easy to provide with a safe running wheel. Roborovski dwarf hamsters are less likely to bite then any other species of hamster.

Cons: Robovski Dwarf Hamsters are the fastest small animal, and can be very difficult to handle. They are not good candidates for small children. Because of their size, you will need a very secure environment for them such as a tank or bin cage that they cannot sneak out of. They need lots of space to exercise compared to their small size and do not take up less room then any other hamster, and you should have multiple wheels if you have multiple hamsters living together.

Mice
Pros: Mice are very easy pets to care for and do not require much more then adequate housing, an exercise wheel, clean food and water. They are social animals and do best if kept pairs, males tend to do better in a larger cage with littermates that were raised together, while females tend to be more accepting of new female mice being introduced. They are very entertaining pets and with the variety of cages with interesting wheels, tubes and mazes they can provide endless hours of antics that are a joy to watch.

Cons: Being the smallest out of all the 'pocket pets' mice should not be handled by very small children who aren't able to be very gentle. They tend to be more skittish and quick moving, although this is generally not a problem with a tame mouse who is handled regularly. It is important to supervise children when they have a mouse out of the cage to prevent it becoming lost...anyone who's ever had a mouse loose in their house will know how hard they can be to find. A frightened mouse is more likely to nip.