Star Wars: Rogue Squadron 2 on the GC one-ups all your stories.

I was pressing a repeatedly o skip through the plot, and an error messege sprung up

"your memory card is corrupted and needs to be formatted. Press a to continue" I pressed a single button and lost all my game saves, no confrimation screen or anything.

Pro-tip. Take the memory card out then ut it back in to fix it :(

Most annoying was definitely Fallout 3 on PC.

Yes; shock. A Bethesda game with game breaking bugs. I was less than 30 hours into the game, but just as I was really getting into it, I ran into a crash that was repeatable on two separate PCs (100% crash rate) that effectively stopped me from progressing any further in the game. At that point, I stopped playing.

Runner up would be when my PS3 60GB died as I had a back up archive made, but since I received a different refurb console from SCE, it was useless.

Lesson learned: make manual copies of any game saves you want to keep. Fortunately, I had many of them copied, but I still lost all my progress on games I had stopped playing.

And while this has nothing to do with corrupted game saves or bricked hardware, probably the worst game save loss in terms of hours logged was on Chrono Trigger (the original SNES version). It was my roommate's copy and he saved over my game save. Supposedly there was a way to transfer saves by popping out the cartridge and then saving on a second one, but I never got the chance to try it out.

My boss gave me a new copy of the game from his shelf of unplayed titles over a year later but I never had the heart to go back and rebuild all my stats. Over 100 hours worth I figure.

Final fantasy 12. I decided to play it on my backwards compatible ps3. I was about 80 hours in, done with all the side quests and levelling up, ready to take on the final mission. I must have quit back to the xmb too fast after saving or something. Next time I tried to load the game it said my (virtual) memory card was corrupt. No way to salvage it, all the saves on it were inaccessible :( Do not turn off your system OR quit back to the xmb while saving....

I watched the final mission on you tube and never used the backwards compatibility again.

Losing a 700 hour final fantasy tactics advance file with level 50s of most of the jobs and all the special characters.

I had a really weird one on RSII... it's not a loss of save data so kinda off topic, but the second time I played the battle of Endor I skipped the cutscene in the middle of Admiral Ackbar saying "we can't repel firepower of that magnitude" and from then on I could never get the last bit of that sentence out of him, he just says "we can't repel firepower of that ma......."

Dragon Age, the game is awesome, but freak, I probably lost like 10 saves due to data being corrupted.  Everytime I'd get to certain parts of the game, the data would corrupt and I wouldn't be able to go an further with that character.

This is one of the main reasons why I hate copy-protected save files on the PS3, you can't back-up your games and if you back-up the whole system to an external HDD, it can only be restored to the PS3 that created it and if that PS3 ever dies, say good bye to all your copy-protected save files.

During the PS1 era, one of my little brothers deleted EVERYTHING from one of my memory cards and I lost a lot of game's data like Vagrant Story, Resident Evil 3, Parasite Eve, Dino Crisis, etc. I decided to start all over again in all games but the only game I couldn't get to where I was at before my save files were deleted was Vagrant Story because I put soooooooo many hours into it, I remember I had the Excalibur sword, max HP, max MP, a super high riskbreaker rank, etc. That really sucked :S

The main reason my I hate Borderlands. Man I loved that game but if I push load I get 3 files labeled as "icorrupt". And they all corrupted when my friends came over to play some co-op  

I eventually just gave up 

I remember being obsessed with Pokémon Yellow. I had invested a lot of time in it when my dear sister decided to delete my save file...I have never touched a Pokémon game (apart from Pokémon Stadium) since then.

Star Fox Adventures was a huge disappointment for me and I swear the bloody game must have sensed my anger and therefore killed my memory card. I lost my save files from Phantasy Star Online, SSBM, Skies of Arcadia, Tales of Symphonia, Eternal Darkness, Wind Waker among others. Rare really left Nintendo with a boom...

Golden Sun Book 2:The Lost Age. Get to the city called Yallam. Go to a specific house, stand behind a specific lady and save your game. Continue later and though you can normally shove people out of the way by walking against them in the game, you can't get out of the spot you're in. Let:wall. Right:Box. Behind:Wall. In front:woman. Teleport doesn't work in houses. Restart file. It has happened to me and someone else I know.

I playedPoP:Warrior Within long enough to get the sand power that creates a sound explosion around you when you're blocking and tap the sand button before I had to return the PS2 to the owner. Now I have a different person's PS2 with PoP:Two Thrones. Played far enough to get the same sand power. Then the memory card randomly corrupts itself and can't be formatted so I can't even start again.