For me, the freakiest stuff is the things that could easily happen down the street or next door to you. I haven't seen "Irreversible" but I've heard, ick. I did see "Happiness", just weird.
The two films I'll add:
"Elephant" - Van Sant's film about a Columbine type of shooting in a high school. I haven't been able to make myself watch that film again.
"Mysterious Skin" - Gregg Araki's film about the results of long term sexual abuse of two boys by their baseball coach. Only seen it once, once was enough.
....we need a smiley with a gag reflex. Ick, ick, ick.
-- spinner