I'm surprised people have not mentioned relays yet. I have always found those to be the most exciting and inspirational. You also get to see the slowest and the fastest people on the relay working like mad. If it is your team then it is all the more exciting.
I saw a 4x400 where a girl was at least 30m back going into the anchor leg. By 250 or so she had taken the lead and then managed to put an additional 10-20m on the rest of the field. I think she split something like 58, but her team was DQed for a lane violation.
Along those lines, UTEP's SMR at the 2008 Texas Relays was great fun to watch. Elias Koech was at least 3 seconds back getting the baton and made up just about all of it, going into lane 5, on the 400 leg. The 800 leg made up the rest of the difference in the first 400 then just pulled away in the last 100. I think Koech split 45 low-44 high.