Surprise packets Castleford and Widnes, who both finished in the bottom five in each of the last two years, are among only four teams with unbeaten records three rounds into the 2014 First Utility Super League.
Winger Richard Owen scored a hat-trick of tries on his first appearance of the season in Castleford's impressive 30-10 win at Hull KR - their first success at Craven Park in the summer era - while Joe Mellor and Rhys Hanbury touched down in the closing minutes as Widnes recovered from 20-12 down to snatch a 22-20 win over Huddersfield.
It was another worrying capitulation for the Giants, last year's League Leaders' Shield winners who began the season with a win at Wigan relinquished a 24-6 lead against Hull KR last week.
Huddersfield coach Paul Anderson said: "We probably need to do some practice closing games out."
Threequarters Jermaine McGillvary and Leroy Cudjoe had scored tries to give the visitors a 10-0 lead but Hanbury and debutant Paul Clough put Widnes 12-10 ahead at half-time and the Vikings responded again after Eorl Crabtree's try and the kicking of four-goal Danny Brough swung the game back towards Huddersfield.
"It is a fantastic win," said Vikings coach Denis Betts. "The confidence they can get from that is immeasurable."
Hull KR took the lead against Castleford at the KC Lightstream Stadium through prop James Green but were then outplayed by the Tigers, whose new half-back pairing of Liam Finn and Marc Sneyd are growing with confidence with every game.
"It was a great performance from everyone out there," said Castleford coach Daryl Powell. "I thought defensively we were superb."
Leeds also maintained their 100% record with a 40-12 rout of Catalan Dragons, a third successive win at Stade Gilbert Brutus.
Rhinos captain Kevin Sinfield, who had been expected to miss the game with an ankle injury, rattled up 16 points from a try and six goals to maintain his record of scoring in all 20 of his club's meetings with the Dragons since 2006.
England winger Ryan Hall scored his first try of the season to draw level with former St Helens hooker Keiron Cunningham in 10th place in the list of all-time leading tryscorers with 138.
On the other wing Tom Briscoe made it five tries in three appearances for his new club as Leeds piled the pressure on Catalan coach Laurent Frayssinous, whose side have lost their opening three matches.