Rats make very good pets.  We have a dozen currently.  They are smart and well-behaved.  You will need to play with them frequently, if not daily as they crave attention.  They are not particularly messy as long as you keep their cage clean on a weekly basis.  Our rats live in a rat condo and we vaccum out the cage daily and clean it thoroughly once a week. 

Rats come in many varieties.  We have regular fancy rats, as well as blue, dumbo, and hairless.