Spoiler Alert: Se7en

Se7en had a very clever plot. Each murder displays one of the 'seven deadly sins'. After you realise there is a pattern you know that there is more murders to come and you are on the edge of your seat waiting for the next murder. It makes you think about how the deaths are going to be linked with one of the sins so your imagination creates it own image of the death. For the 'Lust' death it doesn't show the death due to its potentially graphic nature but it does show the weapon used for the murder so you create your own image. 

Aside from a great plot, the sound is also cleverly done. It has heightened levels of digetic sound so much so that in some points (such as the opening scene between the two detectives on the street) the street noise  almost drowns out the dialogue. This makes the audience feel like they are part of the action by letting them hear what the main characters are hearing. In the dinner table scene where Detective Mills' wife (Gwyneth Paltrow) invites Detective Somerset (Morgan Freeman) over to dinner without Mills' (Brad Pitt) knowledge is dominated by the sound of  the city's trains. This makes Brad Pitt and Gwyneth Paltrow's characters uncomfortable because they used to live in the countryside and have just recently moved to the city. The audience relates to this situation because the level of sound and train vibration is shared by them and so the audience shares Brad Pitt's character's experience of  being uncomfortable.

The final scene in the desert was exciting and I was on edge because of the final reveal. The audience doesn't know whether Mills will shoot John Doe.