A leopard gecko seems perfect. One can live happily in a 2x1x1 vivarium. They come in many different morphs and are very friendly and like a good run around. They are a long term commitment living for around 10 years (and even longer in some cases) they need to be fed daily and some will not eat from a bowl so you have to feed them. They can get sick so vet bills are something to concider. Another good thing is that they are nocturnal so you dont need to worry about UV lighting. Just decent heat mat and stat.
