Adam & Evil
It took me half the movie to even figure out which one was Adam.
Adam was the one harboring a major guilt trip over the fact that 4 years ago, he and a friend set a house on fire with fireworks, killing the family inside. His friend doesn't really give a shit, but he's pretty broken up about it and has flashbacks about it.
Adam and his friends go camping and are killed off, one by one. Is it revenge for their roman candle mishap? Is it the backwoods sheriff? Is it one of the girls' psycho ex-boyfriends? Is it a random serial killer? Although I am fairly sure that the answer is none of the above, I can't say that I am 100% sure of what the hell was going on with the ending - it made abso-fucking-lutely no sense to me.
Total rip-off of every single camping horror movie with a little bit of I Know What You Did Last Summer on the side. Total waste of my time.