I would go for the rat as well. They sleep through the day and are more active through the evening and night. Once socialised they dont bite and are friendly and inquisitive. They eat human food as a treat only and arent grumpy like hamsters are. The eye sight is good so will see you and watch what you are doing and wont scare as much as hamsters when you try to pick them up. When young they will tend to poo and pee outside the cage more but as they mature they get the message of not to do it outside the home. The only drawback is that they will gnaw on anything so you would have to be careful if you leave them to run on the floor.
If you arent going to handle it every day then rats arent for you as they need stimulating to stop them becoming bored especially if you plan on keeping a single rat.
They also like plenty of room in a cage to exercise and need things to gnaw on which if in the same room as you sleep it will get annoying.
Hamsters and mice too are more active through the night so will keep you awake with the relentless activity.
Rats also like to travel around on your shoulder once they are mature and i knew someone who took his out with him when he went to the shops etc.
The gerbil is more active through the day and can also be hand tamed but he is faster than the rat and do better in pairs.
as much as i love hamsters i wouldnt have one again.I had 3 and they were a nightmare.Mine bit and attacked anyone who tried to touch them 
i would go for a rat,mice seem nice though
