One of my favorite places to grab a beer and a snack is a la Mort Subite. Although it does become touristy, it is a civilized class of tourists who like to relax and grab a quiet beer and something to eat, unlike the more popular Delirium Cafe.
The best thing about the cafe, other than the decor and the waiters with attitudes is they make their own beer, and it is strong beer!
If you find yourself in Brussels and want to check it out, just leave the grand place and head to the Gallery St Hubert. Go through the gallery and when you com eout the other side, there it is!