Is this only for gaming, or spoilers in general? If it's in general really ought to be in the off-topic discussion.
This is my non-gaming one:
I ruined the Half-blood Prince for my sister. I told her that Snape was the Half-blood prince before she even started reading. She didn't talk to me for days. She rubs it in my face until now.
My gaming one is:
I accidentally let slip that Cortana died in Halo 4. I assumed that no one even played Halo in my class, as I live in Asia, where Xboxs are more rare than unicorns. Not the biggest spoiler, but it's really the only gaming thing I have ever spoiled.
This is my non-gaming one:
I ruined the Half-blood Prince for my sister. I told her that Snape was the Half-blood prince before she even started reading. She didn't talk to me for days. She rubs it in my face until now.
My gaming one is:
I accidentally let slip that Cortana died in Halo 4. I assumed that no one even played Halo in my class, as I live in Asia, where Xboxs are more rare than unicorns. Not the biggest spoiler, but it's really the only gaming thing I have ever spoiled.