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Wales shocked Fiji and the USA triumphed against England on a superb opening day at the Adelaide Sevens, the fifth event in the 2009/10 IRB Sevens World Series.
The rest of the top seeds all won their matches, hosts Australia, Samoa, New Zealand and South Africa all convincingly, as Friday night's eight games provided the generous Adelaide Oval crowd with ample entertainment.
On Saturday the remaining 16 pool matches will be played and the Cup quarter final line-ups decided, USA and Wales both well placed to reach the last eight.
Pool A
World Series leaders New Zealand scored five tries in a comfortable opening 31-0 win against Scotland.
It was far tougher for Argentina, though, and they needed all 14 minutes to beat danger team Tonga 19-17. The Tongans, who have been receiving coaching from Wallaby legend David Campese, led 17-5 with two minutes remaining but a penalty try got the Pumas back within range and then Joaquin Todeschini converted Joaquin Tuculet's try from the touchline to earn them the comeback win.
Pool B
Last month's USA Sevens champions Samoa won their first match against France. Renaud Delmas scored twice for the French but Mikaele Pesamino also grabbed a brace as the Samoans came from behind to win the first match 33-12.
Nineteen-year-old Sampie Mastriet scored a hat trick of tries on debut for reigning World Series and Adelaide champions South Africa, who started with a 40-0 win against Asia's top side Japan.
Pool C
Wales caused the first upset of the Adelaide event by beating Wellington champions Fiji 17-12. The Fijians led 12-0 early on but tries by Justin Tipuric, Chris Morgan and Darren Daniel clawed it back for Wales as the Fijians were punished for indiscipline with Osea Kolinisau's sin-binning.
Last year's Adelaide Cup runners-up Kenya started with a 27-7 win against PNG, Innocent Simiyu and captain Humphrey Kayange each scoring twice.
Pool D
Arguably the biggest upset of the day, the USA Men began its Adelaide 7s campaign with a 24-21 win over England. Captain Kevin Swiryn led the way, scoring the first and last tries of the match.
England got on the board 40 seconds into the match thanks to a Mat Turner try and Ben Gollings conversion (7-0). Swiryn immediately returned the favor and dotted down less than a minute later, and Nese Malifa's conversion tied it up. As the half neared to an end, the USA's Nick Edwards tacked on another try and Matt Hawkins made it 17-7 with a five-pointer in injury time.
England made its intentions clear in the second half, and Gollings added a converted try during the first minute (17-14). About a minute later, Swiryn put up the winning points with his second try, and Malifa's conversion made it 24-14. England substitute Nick Royle gave England some false hope with a late try, and Gollings' conversion narrowed the gap to three, but the Eagles held onto the 24-21 victory.
The USA faces Australia and Niue tomorrow to finish out pool play.
Hosts Australia then overwhelmed Niue 40-5 in the final match of the day, Kimami Sitauti and Ed Stubbs each scoring two tries.
So far this season there have already been three Cup champions. New Zealand lead the World Series by 14 points thanks to their two opening victories in Dubai and George, but Fiji won in Wellington and Samoa's win in Las Vegas last time out has taken them to up to second place.