I can't really experience fear unless I'm being faced with an immediate threat to my safety and/or security, or if something threatens my loved ones. I know that anything that happens behind the TV screen cannot get me (and the characters in horror movies tend to be unsympathetic). Slasher movies are like slapstick comedy, for me.
On the other hand, it is very easy for me to feel repulsed by images in a movie, book or television show--especially if the images are not staged (like a video of a kid that broke his leg on a trampoline, and had the bone poke through his skin). This can occur from watching a movie that depicts prolonged pain (Hostel), gross-out comedy (the closest I ever came to vomiting while watching a movie was when Chris Ponteas drank the horse semen in Jackass 2) or pornography. The worst stuff is that which depicts violence against children, sexual violence or sadism.
Also, seeing something that appears unnatural can seem very unnerving, to me. There's this hypothesis known as the Uncanny Valley, originally applied to the field of robotics, which proposes that as robots started to appear more like humans, our capacity to empathize with them would increase only up to a certain point, where they might appear human but at the same time not human enough, eliciting revulsion. This hypothesis is now applied to other scenarios such as genetic engineering. A moving corpse is considered to be the most revolting thing to the human mind (placed at the bottom of the uncanny valley). So there are some movies where the visual effects can elicit a disturbance in myself--namely those that utilize clanky stop-motion puppets as opposed to CGI (David Cronenberg's The Fly, The Thing, The Howling). These days, CGI animators try to capture too much detail in their creations, like every blink of an eye or twitch of a nose, which appears too natural to be scary. On the other hand, the creature that Jeff Goldblum transforms into at the end of The Fly moved in a stiff and clumsy manner, and you can still tell it was made of rubber, but it's those unnatural qualities that make it far scarier than the CGI monsters we have today.