Well Malaysia as in city is too small. You can cover the entire city in just 2 to 3 days on foot. All the iconic locations are situated within the city radius. You can get more information about these locations in Google, so I am not wasting your time there. I also recommend to visit the city limits by foot only. Nothing can beat that.
The one and only place I recommend and insist you to go will be the Genting Highlands. Words cannot describe the place. Located at mountain tops, the place is beautiful. One night stay at Genting is compulsory. If you don't visit Genting, your Malaysian trip is incomplete. Plus they have this ancient temple, awesome Ropeway to the top of the peak and a huge mall located at the top of the peak. Huge means Totally Huge.
So hope you have a beautiful trip. Cheers.