Where to start?.....ok...i'll do it like this: Gare Centrale
My favorite spot
Charles Buls fountain- Rue du Marche aux Herbes-Agora Square
St. Hubert Royal Galleries
La Monnaie De Munt Theater
St Catherine & St Gerry
Amadeo: the place for ribs
On the other side of Gare Central
Mont des Arts
Sablon and around
Pierre Marcolini building
Local Belgian - Traditional Brussels
Liege Waffles:"Authentic Liege waffles are one of life's great indulgences-caramelized sugar glistening on a tender, buttery, vanilla-laden joy for the senses. Unfortunately, the "original recipe" has been long lost [...] The recipe that follows is not an adaptation of any other. It's a reconstruction based largely on 18th and 19th-century brioche - which indisputably forms the basis of the Liege waffle (Source)
Visit Brussels describes the local Brussels Waffles as: " Ah, the inviting aroma of freshly prepared Brussels waffles: at the same time, warm, light, deliciously crusty outside and soft inside. They differ from wafers or other waffles that you enjoy cold. For the Brussels waffle, you sit down at a table, you generously sprinkle icing sugar all over it (the waffle, not the table obviously) and if you prefer it rich, you can top it with whipped cream which will slowly melt. We told you, it is bliss."
Now basically, it's up to you what you will enjoy more, but for sure you would need to give both options a try.
Belgians are crazy about comics and you can find loads of shops from where you can buy your favorite strip, from Tin Tin to the Smurfs and so many others, take some time to get in one of the shops...and btw if you are lucky enough maybe when coming to Brussels with Brussels Airlines, you'll get to fly in one of the special planes they have created representing Belgian Icons. Latest one has the Smurfs as a design :)