Thanks for the giveaway! Congrats in advance to the winner (as always, let’s hope I’m congratulating myself here).
As for my favorite pull from a single pack, that is a difficult one, hmm. I did have some amazing pulls as a kid, like Crystal Kingdra or Neo Destiny Shining Magikarp. But since I barely knew anything about rare cards back then, they were just cool because it was crystal and golden, and not too noteworthy in comparison to other Holofoil Rares.
The more memorable pulls I did after I returned collecting in 2015. One was from a Korean CP6 (XY Evolutions) booster box. I had primarily bought the box to just pull a non-holo Common Pikachu for my collection. I bought the entire box, because Korean boxes are very cheap (~15-25 USD for 150 cards), and it’s fun to open up packs. I knew the chances of pulling the other Pikachu in the set, the Secret Rare Pikachu EX full art (which is a Secret Rare in Japanese/Korean, but Ultra Rare in other languages), was very small. I figured I’d just try to buy it as a single later on. So I was very pleasantly surprised and happy when the only Secret Rare pull from the box was the Pikachu EX card I wanted. 
But the most noteworthy booster box opening I did was the Chinese EX Legend Maker box. I will just quote what I wrote when I opened it and shared it in my collection thread:
And here the BGS grades for anyone wondering:
Greetz,
Quuador