One place I would recommend if and only if :-
i) you are seeking value for money tasty hawker food
ii) your priority is to pacify your taste bud rather than ambience to satisfy your ego
-: then Batu Lanchang food court is a nice fit. Especially, the award winning Char Koey Kak and also one of a kind fresh fish pasembor.
I would agree if you never been to Kek Lok Si, your Penang trip is incomplete. However, talking about famous food within that same vicinity of Air Hitam, beside assam laksa another popular food should be the duck Kuey Chap.
Add to the long list of dessert one must savour in Penang is the ABC, personally I like it better if added with banana, makes it all the pleasurable. Also not to be missed is the Mr lobak-lobak, it's bombastic also fantastic with that little meat under a little small stick complement with good sauce to dip = Boomz!