Not in the same league as a few of the above, but in the summer of 2000 AA ran a promo: if you visited all six continents on oneWorld, you'd get a 150,000-mile bonus. For reasons that made sense at the time, I had to do all of it on weekends in July. Fortunately, the 4th was on a Tuesday that year, which gave me a four-day weekend for Asia and Australia. I was also helped along by a business trip to England, which allowed me to pick up Africa (Morocco) on the weekend after.

My total mileage that month was a bit over 40,000. I got 55,000 AA miles for flying (2x miles as Executive Platinum, but "positioning" flights for a Qantas SIN-PER round trip were on Northwest), plus the 150,000 bonus, plus another 20,000-mile bonus for being among AA's top 20,000 flyers that summer: total 225,000 AA miles in a month of weekends. (The NW miles were of little use other than, much later, getting me a bit closer to 1MM status on Delta).