GTA Vice City lets you do exactly the same - run around killing people with no consequences. The best thing is, 2 GB of RAM and 256 MB of video memory are more than enough to run the thing.
Immortals of Aveum has turned out to be an interesting mix of genres, however, it battles a few technical issues. In this benchmark test, you can find out which (laptop) graphics card you will need to run the game smoothly.