I love rats in RPG games, especially since many games mock it now as well as including them. DA is a perfect example, you fight a bunch of rats and your companions says "Its just like the grand adventure tales nan used to tell!". Its kind of like duals in western movies, its cliche, but if done right they are still fantastic
I was going to mention that. I'd love to see a list of RPGs where rats were used as the introduction enemy. I know Baldur's Gate had you fighting rats too.
I think if you're worried about 5 seconds of gameplay in the start of a game you need to go outside more. Rats provide a gentle introduction to newbies and a chuckle for people who have played these games before.