Slim Pickens in Dr. Strangelove.
shown attempts and/or sucesses:
House of Mirth
Nowhere
Storm of the Century
Cookie’s Fortune
Skeletons in the Closet
Prophecy 2 (an amusing suicide, who’d of thought?)
The Ring
Sweethearts
talked about suicides:
Mallrats
Drinking Games
The Man With The Golden Gun is talking about the abovementioned “Swing Kids.”
And how could we have gone this far without mentioning the greatest suicide comedy ever, 1978’s The End, featuring Burt Reynolds, Dom DeLuise, and Sally Field?
Pink Floyd’s The Wall has The main character attempting suicide at one point.
What kind(s) of suicide is the OP-er interested in? Many different motivations and methods…
Enter the Dragon and Shogun feature women resorting to sepukku as a way to save face.
Which Star Trek movie featured Spock sacrificing himself to save the ship?
The Ninth Gate starts off with a suicide by hanging (old man escaping from evil wife).
The '68 James Bond On Her Majesty’s Secret Service features Diana Rigg as a suicidal jet setter who is saved by Bond and eventually marries him.
In The Fly, “Brundlefly” gets Geena Davis to blow his head off with a shotgun. (suicide by proxy/assisted suicide)
The Executioner’s Song is the true story about convicted murderer Gary Gilmore’s successful strategy to get executed – which he preferred to serving life in prison.
Whose Life is It, Anyway? is entirely about euthanasia (really assisted suicide) for a depressed quadriplegic.
In Johnny Got His Gun, Johnny begs for euthanasia, but doesn’t get it.
In Outland, a dangerous narcotic induces miners in outer space to kill themselves by exposure to the vacuum of space.
In The Dead Zone, Martin Sheen’s disgraced politician eats his gun.
In Carrington, Dora C. shoots herself in the heart with a shotgun, out of despair over a lost love.
Dead Ringers, based (but how closely, I dunno) on a true story, ends with the bizarre murder-suicide of identical twins. Drugs and mental illness (or at least drug-induced illness) is definitely a factor.
The Fisher King had suicide as one of its themes.
When Dreams May Come features a suicide out of despair and guilt, and depicts her unpleasant afterlife.
And lots of action and war films show a character choosing suicide over capture/torture/murder/being eaten, etc. – The Bourne Identity, Aliens, Firefox, Red Dawn, etc.
I’m not convinced Major Kong intended to commit suicide.
As I remember it, he was trying to get the bomb bay doors open (“If it harelips everybody on Bear Creek!”) but it took him so long to do so that he didn’t have a chance to get off the bomb before it was automatically released over the target.
There’s a definite look of surprise on Kong’s face when he first realizes what’s happened. Of course, once he does, he decides to go out with style, but I don’t think he planned to commit suicide when he went down to the bomb bay.
I’m surprised nobody’s mentioned Spellbound. You get put right in the head of Leo G. Carroll before he blows it off. Complete with subliminal color flash.
I wouldn’t call Kong’s death a suicide either. Of course, it’s still one of the most memorable deaths in all of film.
?? You got a problem with this movie? You better take it up with me, buster, cuz them’s my girls!
The first movie that came to my mind was Lost and Delirious. I won’t ruin the movie for you but there is a suicide involved.
The Elephant Man has a particularly moving suicide and a fairly disturbing depiction of the reason for it.
Of course, like so many GenXers, I’m familiar with Johnny Got His Gun through Metallica’s One video. That Johnny is about a basket case asking for death, is fairly common knowledge.
Sadly, I've never found a copy of the film for rent.
I did find a copy of the book. But, I always quit at about the 50 page mark. Scattered throughout 40 plus pages of reminiscing about his childhood are a few pages in which the soldier begins to realize just how injured he is.
But now, thanks to you I can finally just chuck the book. I can abandon my search for a rental copy of the film. For years I've hunted for this film like a bottle of rare wine. Ah, the anticipation. The way I'd planned to savor each sip. But now, you've saved me the trouble. You've handed me the empty bottle and told me that the wine was good.
I simply had to take the time to thank you for doing me such a wonderful service.
“Brother” - yakuza gang movie. Gotta love the suppuku(sp?).
“Deer Hunter” - russian roulette
Godfather II
Pentangeli slashes his wrists and dies, ancient-Roman style, submerged in a bathtub.
C’mon, then, babe… let’s take it outside. 'Cause I’m ready for ya. 
The scene in Last of the Mohicans always gets me, although it might just be the beautiful scenery.
Girl Interrupted(not successful)
and sorry Stoid but Thelma and Louise terrible
Once Upon A Time In The West
Ends with one of the stupidest suicides of all time as a lead character (James Woods) oh-so-symbolically throws himself into the back of a garbage truck, presumably to be squished to death.
Shit. I meant Once Upon A Time In America. The spoiler is for …America.
Gee whiz, two pages and no one’s mentioned One Flew Over the Cuckoo’s Nest? (B-B-B-Billy.)
Also, Mississippi Burning, and The Heart Is a Lonely Hunter.