Personal Experience: This is probably one of the weirdest movies I have ever seen.
Production date: I have seen this movie at least 5 years ago. Obviously produced after 2001.
Plot: A group of 5 friends (at least) get lost in some forest (or exploring). And they find this modest house in the middle of nowhere to seek shelter. They find a happy, healthy (apparently) living old couple who give them the best hospitality. The couple invites the group to stay in their house for the night. Few moments later, the movie gets very disturbing, the couple start killing those young people one-by-one in different ways, and they were very happy and calm. They manage to kill them all besides one person who will manage to kill later the old wife.
How it ends: The old man goes outside of the house after his old wife is dead. The murderer puts his hands in the sky and shouts "Why God! What did I do to you". Clearly some subliminal message from the director.