I should start by defining my metric for top 5. Basically, it's the world records that I personally find the most delightful and charming, not the most serious or impressive (although some of these really are impressive!).
In no particular order, here are some fantastic ways Lubbock's been the biggest and the best.
Perhaps the most endearing annual event in Lubbock, the Lion's Club Pancake Festival is also the biggest in the world. This family-friendly event always fills me with joy: the mascots, the balloons, the mariachi band and over 65,000 pancakes served per year! And it raises around $100,000 for a very worthy cause.
At nearly 11.5 metric TONS, Lubbock's own Bahama Buck's created the largest snow cone in 2011. The flavor was birthday cake, and proceeds raised by the event went to The Children's Home in Lubbock. Neat!
Even louder than the guy next to you at the stop light
In 2005, Lubbock's Custom Sound Works created a stereo so loud it was only 16db from being the loudest something can actually be. And 16db is not loud at all - less than the ambient sound of a recording studio with nothing going on. The doors had to be bolted shut and there was actually very little room for people to actually fit in the van. Not that you'd actually want to be inside of it at full volume anyway.