More seriously, my favourite view of the Petronas Towers is from the Skybar at Traders Hotel, decently priced cocktails too.

KL is dirt cheap and the food is incredible. Obviously go check out the caves on the outskirts of town, otherwise go on a food tour if you can. It's a Muslim country so some restaurants do not serve alcohol, but overall it's a very liberal Muslim country.
The airport is a bit of a pain because it's
so far from central KL and there's an annoying arrival situation where you have to bus over to immigration. There's a form you need to fill out online before you arrive and be prepared for a pretty hefty wait to get through immigration, it can get really bad. Once through, there's an express train that takes you to central station, otherwise it's between 1-2 hours in a Grab (for like $7).