Eighteen-year-old Kirani James stunned defending champion LaShawn Merritt to win the 400m gold and secure Grenada's first medal at the World Championships.
James, who has run just a handful of senior races after many junior titles, surged past Merritt just before the line for a personal best of 44.60.
David Rudisha, unbeaten since the 2009 Championships, won the 800m in one minute 43.91, Abubaker Kaki second.
Fabiana Murer won the women's pole vault, with Yelena Isinbayeva sixth.
Two-time Olympic and double world champion Isinbayeva had looked in good form in the heats, albeit landing just one vault at 4.55m to qualify.
The 29-year-old, whose world record stands at 5.06m, came in at 4.65m and sailed over. Passing at 4.70m, she then bumped the bar off at 4.75, but rather than retrying at that height went up to 4.80.
Her first attempt at 4.80 was no better, brushing the bar with her stomach, and a final attempt at the same height saw the livid Russian not even get close to the bar and she left the stadium muttering angrily to herself.
Brazilian Murer, who was fifth at the World Championships in Berlin two years ago, managed a best of 4.85m, with Germany's Martina Strutz taking silver and Russian Svetlana Feofanova winning the bronze.
The 400m produced a classic finale as Olympic champion Merritt, recently back from a 21-month ban for doping, came round the final bend with what looked like a comfortable lead.
However James found a stirring finish leaving Merritt to settle for his second World Championship silver medal in 44.63 with Belgium's Kevin Borlee, whose twin Jonathan was fifth, claiming bronze in 44.90.
In the women's 1,500m, Britain's Hannah England reached the final as a fastest loser after a battling finish down the home straight saw her finish sixth in the second semi-final, recording a time of four minutes 8.31 seconds.
The men's discus was won by Robert Harting of Germany with a throw of 68.97m, Estonia's Gerd Kanter claiming the silver after 66.95m and Ehsan Hadadi (66.08m) the bronze, while Britain's Brett Morse was 12th after throwing 62.69m.
Yuliya Zarudneva of Russia won the women's 3,000m steeplechase in a time of nine minutes 7.03 seconds, comfortably ahead of Tunisia's Habiba Ghribi (9:11.97) and Milkah Chenos of Kenya (9:17.16), while Briton Barbara Parker finished 14th in 9:56.66.