Annie's is a nice, owner-operated little water ice shop - not part of a big chain. They have water ice, custard, and make mixes (like the gelatos and other concoctions you find at Rita's Water Ice). The water ice is a a bit more flavorful than Rita's.
The location is a little out of the way - across from the Doylestown train station. IT's a good local place, and fun to take the kids.