probably the closest I've had to predicting a dice roll is when I was playing D&D and we tried to craft a resurrection potion while stranded in the middle of nowhere. I briefly thought about saying its a bad idea and impossible, but my gut told me not to. The ranger goes over and nat 20s, finds some magic 4 leaf clovers. The dm implies it would take a "miracle" for it to work after we craft it, so we do a d20 luck check and ofc nat 20s, dude is revived after being dead for 90 minutes, everyone starts popping off, it was a great day