Nice happy title, right? :) Being in the field I'm in, I've been educated about suicide more than the average person, which also means I get annoyed more than the average person about misperceptions about suicide.
Suicide is a major taboo, even though many inroads have been gained over the years. An excellent example has been Dr. Robert H. Schuller's response to his friend's suicide a few years ago. Traditionally, Christianity has stated that suicide means a straight line to Hell. Schuller has nicely reframed it as a "cancer of the mind," providing a new way of looking at a horrible situation that gives us a new way to look at our theology. I could say more about this, but it is an interesting topic to struggle with, and I encourage everyone to do so.
I've noticed two in particular that have irritated me a lot. They often happen in the media, so they may not be representative of the general population, but still:
1. Did he/she leave a note?
This is often asked from a skeptical loved one who cannot believe the individual committed suicide. The emotions are fair enough, as is the desire to find any way of debunking the possibility that the death was by suicide. However, most people do not leave suicide notes. Some do, but as satirized in Analyze This, such notes are not definitive of suicide. The presence or absence of a suicide note does not give absolute proof of suicide.
2. But he/she wasn't depressed!
It's amazing how well people can hide depression (it doesn't always look like sadness). But beyond that, suicide is not always caused by depression. Depression is a major cause, but there are many reasons a person may commit or attempt suicide. Sometimes death is even accidental. Some of the other mental illness-related causes of suicide are a manic episode (for instance, a man believes he can fly and so jumps of a freeway overpass to his death--it's suicide, but he wasn't depressed). During a psychotic episode, people can also commit suicide, again for a variety of reasons.
There are volumes and volumes of work on suicide, so if you are interested, do some research. But in any case, please don't assume someone who committed suicide was depressed and left a note. It's a LOT more complicated than that.
If you or someone you know is contemplating suicide, please seek help right away. New Hope is an excellent resource. They can be reached online at that link or by phone at (714) NEW-HOPE or (714) 639-4673.