I am completely freaked out and scared because of the game 'Slender'.What is the scariest game you've ever played?

My friend linked me the game Slender (Link: http://www.mediafire.com/?qg48g5aaed61bi2)

Normally I can play horror games, get scared, and the laugh it off. Not this one. I physically feel different. I'm tense, paranoid and just plain freaked out.

I'm not finding pleasure in the things I do now. Food still tastes good, but I don't enjoy eating it. Talking to people is just a chat. I barely laugh at things funny. It's been about 3 hours now and I haven't changed. It's like the game has completely altered my mental state. I don't even want to think about what I'm going to dream about tonight.

I'm wondering, what is the scariest game you've ever played? And a bonus question. Have you finished the game 'Slender'?