No matter what the year, every summer season tends to deliver one or two unexpected hits.  Sometimes it's a movie Hollywood thought would do well, but explodes into something more ("The Hangover").  Often it's an inexpensive indie that comes out of left field to become an actual hit with snazzy profit margins ("Napoleon Dynamite," "The Blair Witch Project").  So far, the summer of 2012 doesn't appear to have any surefire surprises on the horizon (if you don't want to count the shocking mammoth haul for "The Avengers"), but a lot could happen over the next three months.  Looking for some surprises, the HitFix staff scoured the record books and came up with 15 of the most unexpected summer movie hits of all time (well, maybe the last 30 years).  Granted, there are others, but these films definitely fit the bill.

Find out which ones made our list and why in the gallery below.