Can someone please give me some REALLY scary movies?

Exorcist... guaranteed one of the best horror flicks of all time. Insidious is right up there...haven't seen it but getting soo much buzz from friends and the damn trailer is insane. Now you might have to look this one up.. it was called puppet masters... not the weird puppets.. this one had donald sutherland in it.. aliens takeover and the people are the hosts... ******* unnerving ... the aliens suckshon on to the people necks... its crazy and a classic