The first Saturday of May each year is Free Comic Book Day. As a way to get more people to read comics (it's not just for kids!) and also to promote some comic series you may not have heard of elsewhere, FCBD is always a huge hit. Stores across the city participate and I would suggest going early if you want the best selection. Many stores will limit you to a selection of 5 comics per person. Some of my favorite comics to read are Archies, Disney and Sonic the Hedgehog.
Check out their website here to learn more about Free Comic Book Day and to locate stores that are participating.