American Walter Dix threw down the gauntlet to rivals Usain Bolt and Tyson Gay by powering to victory in 20.06 seconds in the men's 200m at the year's opening Diamond League meeting in Doha.
The time set by the double Beijing Olympics bronze medallist was a world best for 2011 and a meeting record.
Britain's Michael Rimmer was second to Asbel Kiprop of Kenya in the 800m.
American Allyson Felix edged out Botswana's Amantle Montsho to win the women's 400m in 50.33 seconds.
Pre-race favourite Felix, the three-time world 200m champion and Beijing silver medallist, was forced to battle to the line for her win having come under serious pressure from the Commonwealth champion, who was second in 50.41.
Felix said she had yet to decide whether she would take part in both the 200m and 400m at the World Championships in Daegu in August.
"It's definitely something I'm considering," said the 25-year-old.
Meanwhile, Dix warned his rivals that "everyone is beatable" after recording his impressive 200m time in the first of 14 Diamond League meetings this season.
The American eased to victory in the absence of compatriot Gay and men's Olympic 100m and 200m champion and world record holder Bolt, who will kick off his Diamond League campaign in Rome on 26 May.
"Walter Dix is reloaded!" said Dix. "I started the season very strong and that was a great opener. I didn't train in January and missed the indoor season but now I feel very strong.
"I'm aiming high in Daegu and I can tell you that everyone is beatable."
Meanwhile, BBC athletics commentator Steve Cram said that Southport-born Rimmer, 25, "had probably made one of his best starts to the season" in finishing second to Kiprop.
Rimmer recorded a time of one minute 45.12 seconds, with Kiprop setting a season's best of 1:44.74.
France's Teddy Tamgho eased to victory in the men's triple jump with a winning leap of 17.49m. Leevan Sands of the Bahamas was second ahead of Cuban Alexis Copello in third.
And there was a huge cheer from the Ethiopian support inside the Hamad Bin Suhaim Stadium when their athlete Yenew Alamirew won the men's 3,000m in 7:27.26, making him the ninth fastest of all time over the distance.
Elsewhere, there was a surprise in the women's 100m hurdles, with American Lolo Jones beaten into third by winner Kellie Wells [12.58] and second-place Danielle Carruthers [12.64].
Jones, who has been suffering from sciatica, recorded a time of 12.67.
The 28-year-old later tweeted: "Oh sensai, I have failed you coach [Dennis] Shaver. I did exactly the opposite of what you told me. Your student will do better next time."
Another shock came in the men's pole vault with Frenchman Renaud Lavillenie, who set 6.03m in winning European indoor gold in Paris in March, failing to progress beyond 5.50m.
Germany's Malte Mohr won with a vault of 5.81m.