No visit to the strip district is quite complete without a small bag of the Chicago mix popcorn (at the very least). The selection of popcorn changes weekly, and the various locations have different offerings during the same week, so check the website to see which location has the flavor you're craving.
The Chicago mix is a blend of the cheddar and the caramel popcorn that strangely works, and is always on the menu.
A few of their not-always-offered varieties I HIGHLY recommend, if you are lucky enough to see them:
Rice Krispies Treats
Chocolate Pretzel
Chocolate Waffle Cone
Dark Chocolate Blackout
*** Peeps **** -- Best flavor ever. ONLY available near Easter, as apparently the darn things are very difficult to melt without burning.