So I finally just beat hard core mode and got my foam finger.  It took a lot of time getting through the game, but even more time was wasted after dying partway to a save point.  Since it sets you back hours at a time, each death on hard core is memorable, so share your failures here.
 
 Death 1: insta-killed at full health by the slasher that spawns where you first get stasis

Death 2: I backed myself against the door of the train compartment after starting it up only to be grabbed from behind and get a full on french kiss from a puker

Death 3: Killed by a lone slasher (ninja necro) that kept dodging every one of my shots

Death 4: I kept missing stasis shots on, and getting pounced on by, the boss (arguably) at the end of chapter 1

Death 5: I was killed by necromorphs continuously spawning out of a vent at the stalker (is that what they're called?) in chapter 6

Death 6: I had a rough landing on some debris at the end of chapter 7

Death 7: killed by an already dead puker at the daycare center entrance

Death 8: violated by a gang of preschoolers and newborns in the daycare auditorium
 
Death 9: ...goddamn decontamination room...
 
Death 10: I killed myself while playing with the arm of one of those suicide guys
 
Death 11: overwhelmed by the super necromorph, 2 infectors, and 2 advanced slashers.
 
Some useful stuff I learned along the way:
Most spawn points are the same every time, including when you're hanging upside down from the train
You don't get sucked out a window if you're in a different room when it blows out.
Stalkers take turns running at you (only ever one at a time)
Those nest things (in zero-g) can be dealt with by charging at them and tearing apart all 3 nodes with a single ripper blade
You can use kinesis to grab a puker's projectile vomit ball and throw it back for an insta-kill
At the end of chapter 7 when you're back on the ground and being attacked by endless enemies, if you don't kill the first few pack that spawn and just run around the area, you can just keep running laps until the door opens
Stasis + Line gun secondary = dead brutes

ive not played hardcore but most of my deaths if not all come from accidentally breaking windows and forgeting that even though it looks pretty nice its not a cutscene.

Died in chapter 11 when I wasn't being cautious because it was an easy part. It was the room where some lurkers are below you along with some red cylinders. You're on a suspended walkway and as you walk along enemies (dark) spawn in front and behind and there's a power node on some mesh just to the side of the path. Got one hit killed when a dark came from behind. Died a couple of times at the end but I had saved just before so not a big biggie

I did really well until the later parts of the game:
 
 

• Died in the deconamination chamber.
• Died a couple of times in that big room in the mining complex.  Got snuck up on a lot.
• Died once stupidly running right into the side of one of the spinning lasers.  This was my second worst death because I was originally planning on using my last save sometime after that section and had to go back to chapter 10.  I ended up saving at chapter 13 near the beginning of GovSec.
• Died once in the final Zero G area when one of those projectiles knocked me backwards into a beam.
• And my stupidest death of all, I flew into a piece of debris trying to get to the gunship.  I was really pissed after that happened and had to take a break for a few days before coming back and finally beating it.

I actually started this yesterday and have had two failed attempts. My first "death" was right at the entrance to the nursery in chapter 6. I paused to go grab a drink and the power died, shutting off my Xbox. Fun stuff. 
 
I waited a few hours and then decided to give it another go. Since I'm playing on 360 and get a free checkpoint at the disk swap (score one, inferior hardware), I was waiting to save until the harder chapters towards the end. I was doing well on ammo and med kits at the end of chapter 6 and had just got done killing a Brute. Brimming with confidence I walked into the next room which (if memory serves) is the room with the elevator where the disk swap takes place. In that room was a wall-mounted necromorph who shoots out little pods that sprout a tentacle capable of shooting you. I decided it would be a smart move to try stomping on the pod instead of shooting the tentacle to conserve ammo and it exploded, one-shotting me. I had stomped on these guys in the past and never had that happen to me before >< 
 
I don't know if I have it in me to try again just yet. I know I can handle it but I'm too stubborn to save before chapter 9 or 10 so its more of a mental struggle than anything.

Felt like I could make it to the 2nd disc without saving so I died 5 times trying. Died on really dumb places which I would have never before. Like the beginning after the dude wakes you up and his face explodes, was smacked down by the first necro on the left.

On my 6th try I made it. Saved in chapters 8, 10 and 12. Died once in the decontamination chamber.

I haven't played hardcore mode yet,  but so far I've found the most difficult bits as follows: 
1)  When you eject from the solar array, I got splattered countless times playing that on Zealot, would probably have to make the save point right before :) 
2) When the tramlink stops and I got out to clear the path, the room with all those annoying chargers took several tries :( 
3)Ishimura right before the cursed gravity thing in engineering, that corridor... a slaughterhouse! 
4) The Zealot is manageable if you have tons of Javelin ammo.

You 360 version owners and your disc swap autosaves...

I haven't completed it yet, though these were the finales of each of my three attempts, none without any saves since I figured they deserve to be withheld until the ending stages where it'll get downright insane. 
 
Death 1 - Cyst explosion, during the travelator area just before you meet Ellie. 
Death 2 - One of those explosive arm SOB's spawned literally right behind me and killed me before I even had a chance to notice. 
Death 3 - Same area, except I had to reload when one of those explosive arm necros was lumping towards me so I tried to run instead. The radius on that fucking thing is bafflingly large.. anywhoo, that's not what killed me. During the animation of being knocked away, I was hit by a standard necro which killed me. 
 
Fun times!!..

I got killed at every single instant kill part in the first 3 acts and rage quitted

" You 360 version owners and your disc swap autosaves... "

The deaths I remember from hardcore...
 

• Died from an explosion guy during the upside down train sequence.
  
• The main hall where the necro's overwhelm you after the Solar Array section.
  
• Pregnant necro hiding around a corner right before the tram to the Ishiumura.
  
• Eye poke machine. I passed it on my first play through by luck apparently. 
• The last Zero-G part by one of the fire exhaust.
  
• The Tiedeman stand off sequence because one of my cats stood in front of the TV. I did hit the "A" button, but not quick enough. 

 On the plus side, the final boss was cake with a fully upgraded Contact Beam.

I had a smooth start and rocky end, but overall remarkably few deaths, all of which happened after my second save (chapter 8)
 
* Death by fire in the zero-G section after the guy turns on the machines (fighting one of those 3-pod growth guys, he pushed me back into a ring of fire)
* Died to an exploder a little while later, near the last breakable glass in the game (I was avoiding shooting at the glass and didn't see him approach).
 
Then saved again in chapter 12, right before the drill, and:
 
* Died to the eye poke machine - grrr
* Died in the last zero G section in the game, knocked back into the crushing hazard.
 
Got frustrated and decided to reload my 2nd save (chapter 8) to move my 3rd save further into the game (saved right before the room with the lasers in ch. 13) and beat the game that try :P.
 
Definitely a much more tense way to play the game.  I enjoyed the run, but I was sweating bullets at every instant-death hazard that was more than 3 chapters from my last save, even "mash A" QTEs.