well assuming you know your problem areas i guess with 1 week left you can either do lots of problems or do more CATs. I prefer problems since if i do bad in CATs it might affect my mood on test day. you can also go over simple basics like idioms etc. Do you have any gmat books to study from? At this point it is probably not a good investment to get a new book but make sure you go over your current books - maybe go back and redo questions you got wrong before..
If you like my answers please +1 kudos!