My district's high school does something before prom that I like. About 4 kids are designated Grim Reapers. They dress up, wear make-up, the whole thing. During the day, they visit a variety of classrooms. They stand menancingly in the back not saying anything until they pick their target. Then, they walk up to a student, point at them, and motion for them to come with them. The student and Reaper leave the room. The student then gets a black t-shirt with "Dead" written on it and they have to wear the shirt for the rest of the day. The dead are not allowed to speak for the rest of the day, either.
The Reapers pick about 37 students to be dead for the day (~1% of the student body). At the end of the day, there is an assembly about drunk driving accidents on prom night and the whole thing.
From what the students tell me, they find it very moving and unforgettable to think of their friends "dead" on prom night.