9 Basic Lands in a row!
Look - I get that random means random. But in the analog world, I've never lost anywhere near as many games as I lost today due to mana floods consisting of anything from 5 to 9 basic lands in a row. At one point in round 3 of today's qualifiers, I'm ahead in every measurable way. Until I drew 9 basic lands in a row from a deck that had 11 or 12 left and 20 other cards.
I know - it's just random. But I lost 4 qualifiers today because of floods. I played great games against great opponents. I won some and I lost some. And every game where I didn't flood, was either a close loss or a win. This last one just hurts, though. I was at 30-something life. My opponent was at 11. He drew removal and creatures and great spells. I drew lands. I don't care how good a player you are, or how good your deck is. Pulling 9 basic lands in a row will end you.
I should probably stick to the analog world, where when I shuffle my deck, my goal is distribution, not randomness. Randomness kinda sucks sometimes.