Not a day goes by that I don't think about the rare bug that used to let you accidentally disassemble yourself into tinkering bits, with the message, "you are destroyed. Great job!"
D&D 3E had a system where you would threaten a critical hit, then roll to confirm. A house rule I came across was a 3rd roll: 20 to threaten, then 20 to confirm, and you could roll again, one-shotting on a third 20.
This rule also included critical fumbles, where if you rolled 1, then 1, then 1...
"Oh cool this is the game that lets me wear faces for stat bonuses. What if... I put my own face on my face? And then that doubleface atop my own face once more?"
Comments
This rule also included critical fumbles, where if you rolled 1, then 1, then 1...
....
Ooops."