Dave Chisnall knocked reigning partypoker.com World Grand Prix champion Michael van Gerwen out of the tournament with a thrilling 3-2 quarter-final victory on Friday night, as Phil Taylor, James Wade and Justin Pipe also won through to the semi-finals in Dublin.
World number seven Chisnall produced arguably the finest performance of his career so far as he hit ten 180s and held off Van Gerwen's fightback from two sets down to rally and claim a five-set victory.
The St Helens ace will now play Pipe for a place in Sunday's final at the Citywest Hotel in Dublin, but was able to savour a memorable win over the Dutch star.
"Michael didn't play his best darts and even when he came back I felt I was scoring better than him" - Dave Chisnall
Chisnall left the reigning champion reeling by taking the first set without reply, hitting 180s in all three legs, before taking the second set 3-1 by continuing his brilliant start.
Van Gerwen began his comeback by winning the third set 3-2, taking out a superb 127 finish in the deciding leg, only for Chisnall - a former Lakeside Championship runner-up and UK Open semi-finalist - to land an 11-darter as he moved 2-0 up in the fourth set.
Van Gerwen hit back to level as Chisnall missed one match dart, at double 16 in leg four, before the world number two took out 92 to win the set and level the game.
Chisnall, though, steadied himself by winning the opening two legs of the deciding set in 13 and 15 darts, and after Van Gerwen won leg four, he posted a tenth 180 of the game and finished double ten to seal a fine victory.
"I'm over the moon, I can't believe it," said Chisnall. "This is my best win because I knew that if I produced what I can do then I'd have a chance, and I played well.
"Michael didn't play his best darts and even when he came back I felt I was scoring better than him. I'm really happy to be through and I've not shown my best yet - but that was close to it.
"You have to have a good start against Michael because if you don't, he'll get confidence from you not hitting your doubles, but I was building confidence from him not hitting his doubles.
"I've beaten Phil Taylor in the World Championship before and now I've beaten Michael here, so I've shown that I can beat the two best players in the world."
He added: "I'm going to take one step at a time, relax on Saturday and see how I go on against Justin. I've played Justin a lot of times before and I'll just focus on my own game, but it will be one of the biggest matches of my career."
Pipe's earlier 3-1 win over Andy Hamilton put him into the semis against Chisnall - with the winner not only guarateed a place in the World Grand Prix final but also a spot in next month's William Hill Grand Slam of Darts.
Pipe, who had not dropped a set in his victories over Andy Smith and Adrian Lewis, also won six of the game's first seven legs as he took a two-set cushion against Hamilton.
The UK Open finalist hit back to take the third 3-1, but Pipe won the fourth set in a deciding leg to seal his place in only a second major televised semi-final.
"It's a massive win for me. We're both grinders and I've learned a lot from Andy, and I'm so happy to beat him and reach the semi-finals.
"I think it's the biggest win of my career. Last night was massive to beat Adrian, and this is huge - it means a huge amount to me to be in the semi-finals. It shows how far I've come in the game in the last three years.
"I've got a big task in the semi-finals and it's going to be hard to beat Dave - but I can do it and I'll be confident."
Pipe had endured personal tragedy earlier this year when his brother Mark passed away suddenly in June, and he added: "Losing Mark was very hard and it would be amazing if I could win this tournament and dedicate it to him because he's a driving force for me."
Today's other semi-final will feature ten-time World Grand Prix winner Phil Taylor taking on two-time finalist James Wade.
Taylor booked his place in the last four with a comfortable straight sets victory over Gary Anderson with an imperious display.
The World Champion took the opening set in 12, 13 and 13 darts and took the second set 3-1, and though Anderson kicked off the third with a 160 finish, Taylor won the next three legs to seal the win.
"I wanted to lay down a marker and it was important to win that first set and put him under pressure, which I did," said Taylor. "It was a tough match but Gary missed a few crucial doubles and let me off.
"Gary's a great player, world class, and I want to shake him sometimes! He could be better than me, he's a better 180 scorer and when he hits his doubles then you might as well go home, but I took advantage tonight."
Taylor added: "It will be tough in the semi-finals but I'd love to go on and win this tournament now.
"James is there and thereabouts in every event and it's probably better for me to be playing him because I know what he's capable of. I've played him many times so I know what to expect."
2007 and 2010 champion Wade showed his class by twice coming from a set down against Simon Whitlock before winning a sudden-death leg in their clash with a 101 checkout.
"Maybe I was a bit lucky but I hit the right shots at the right times, and that's a good sign" - James Wade
Whitlock took the first set 3-2 before the left-hander won the second 3-1 to level, landing a 106 finish along the way, only for the Australian to punish his missed doubles by sweeping through set three without reply.
Wade, though, took out 160 as he won set four in a deciding leg, after Whitlock missed the bull to claim victory, as the game went into a fifth set.
Whitlock led 2-1 to move once again to the brink of victory, but Wade hit two 180s in a 12-darter to send the game into a one-leg shoot-out before progressing to the semis with a 101 checkout.
"I'm very happy," said Wade. "Maybe I was a bit lucky but I hit the right shots at the right times, and that's a good sign.
"I'm making myself dig deep; I'm not starting off with big shots but I'm due a good game and I'm looking forward to the semi-finals."
The format for the semi-finals sees the games extend to the best of nine sets.
Dave Chisnall v Justin Pipe
Phil Taylor v James Wade