Erin/Lyndsy?
Im assuming you are speaking of womens closing speed with the name you gave yourself. You would probably want to research the Ethiopian women. The top few have been able to close in under 60. As far as the men are concerned, you would want to look at Bernard Lagat. He closed in 51 on a 1259 race. Running a fast last 400 is one thing but running one off of a fast pace is something entirely different. Bekele, yes, as the other poster mentioned has also closed very well. But in my opinion, the fastest has been the Kenyans Isaac Sangok and Abraham Chebii. Both have also run 51 and 52 second final 400s at the end of fast 5Ks.
Sic Em'