I'm going cop. And I will patrol the streets all night long. Doh I hope I can end the night with a whore and some beer. =P
If it's just kill, kill, kill then it might be a little bit boring.
I hope it have a lot of options to do. Like street race, drugs, whores, banks, your own house or apartment etc. Like GTA but with even more freedom.
And I hope there is somekind of reward doing your work. If it's just a point system then it will be a bit boring. Again something like GTA, get the cash buy some new stuff and so on. Some goals to fight for are nice in a MMO.